Author: Abi Saeed

Abiya (Abi) Saeed is the Extension Horticulture Specialist at Montana State University, located at the beautiful campus in Bozeman. She has a background in entomology, pollinator conservation, and integrated pest management. She received her Master's degree in entomology at the University of Kentucky and is currently working on her PhD in Plant Sciences at Montana State University where she is doing research on urban pollinator conservation. Prior to Montana State University Extension, she has been a horticulture educator at Michigan State University Extension and Colorado State University Extension. Abi is also a recurring panelist on Montana PBS's weekly live call-in TV show: Montana Ag Live.

The Spooky and Spectacular World of Carnivorous Plants

As a lover of the weird and wonderful, October is one of my favorite months of the year, because of Spooky Season. To celebrate, I thought it would be fun to learn about some of the weird and wonderful plants around us, especially some of the most notorious: carnivorous plants.

Whether you like to grow them, observe them in their natural habitats, or simply just learn about them, it’s easy to understand our collective fascination with carnivorous plants. Many of us may have seen depictions of ‘man-eating plants’ in horror movies, or exaggerated tales of some of these killer plants in fictional stories, cartoons, and other pop culture references. The horror genre’s elaborate and embellished portrayals of carnivorous plants were inspired by Charles Darwin, before which plants were considered to be innocent bystanders to the ecological phenomena surrounding them. Having spent 16 years researching carnivorous plants, Darwin published multiple books about them. This shifted our perception of plants as a whole and how they interacted with other organisms, giving rise to our fascination with carnivorous plants, driving our desire to understand their biology, and fueling our creativity by exaggerating some of these adaptations into very entertaining science fiction. I wonder If he could have ever imagined the creative ways in which popular culture (especially science fiction and horror) would go on to embrace these botanical marvels.

Types of Carnivorous Plants

Carnivorous plants are defined as plants that extract nutrients from animals. These plants have a variety of adaptations that allow them to capture and/or trap prey (most often insects and other arthropods), and enzymes that can break this prey down into nutrients that can be used by the plants themselves. Although carnivorous plants do still perform photosynthesis, they get most of their nutrients from captured prey.

Venus fly trap (*Dionaea muscipula*). Photo: Karelj, Wikimedia Commons https://commons.wikimedia.org/wiki/File:Dionaea_muscipula_Exhibition_of_Carnivorous_Plants_Prague_2015_1.jpg

Some of the more famous carnivorous plants include the charismatic Venus fly trap (Dionaea muscipula), the North American native pitcher plants (Sarracenia spp.), the tropical vining pitcher plants (Nepenthes spp.), the widespread sundews (Drosera spp.) and butterworts (Pinguicula spp.), and the moisture-loving and often aquatic bladderworts (Utricularia spp.). Some not as well-known examples include a few species of carnivorous Bromeliads (in the genera Brocchinia and Catopsis), and Triphyophyllum peltatum that can become carnivorous in situations of nutrient scarcity, after which it may revert to a non-carnivorous lifestyle. There is also a plant called the Gorgon’s Dewstick (Roridula gorgonia) which captures insects, but lacks the mechanism to digest this captured prey. Instead, this fascinating plant will trap this prey to attract the jumping tree bug (Pamerida spp.) which feeds on these trapped insects, while leaving nutrient-rich frass (insect poop) which is absorbed by the leaves of this plant!

Sundews (*Drosera* spp.) use the sticky tentacles covering their leaves to trap and digest insect prey like these damselflies. Photo taken in Duck Lake, Oregon, Source: Noah Elhardt, Wikimedia Commons https://commons.wikimedia.org/wiki/File:Drosera_anglica_ne2.jpg

The ways that plants actually capture their prey are pretty diverse: ranging from sticky substances that can immobilize prey, dark tubes and funnels that can trap and disorient them, and mechanical methods that can snap/ensnare or suction prey, dooming them to their fate. These mechanisms are defined as ‘active’ or ‘passive’ based on whether there is movement involved in the prey-capture process.

Evolution of Carnivory in Plants

Although we previously lacked a deeper understanding, advancements in molecular biology have allowed us to paint a more complete picture regarding how plants actually evolved this interesting adaptation.

Carnivory in plants is another classic example of convergent evolution (where unrelated species independently evolve similar traits), with instances of its occurrence over 12 different occasions across the evolutionary timescale of flowering plants (angiosperms). We currently estimate that carnivory is evident in over 800 species of plants across more than a dozen plant families.

Bladderworts (*Utricularia* spp.). Photo: Nativeplants garden, Wikimedia Commons https://commons.wikimedia.org/wiki/File:Utricularia,_Paithalmala_2.jpg

All of these instances of carnivory were driven by similar needs: limited nutrient availability in the habitats in which these plants grow. These carnivorous plants grow in conditions which lack specific nutrients essential for plant growth (many of which include bodies of water or soils that are low in Nitrogen and Phosphorous). Arthropods such as insects can be excellent sources of these (and other) essential nutrients, and are often abundant in these habitats…all that plants needed to do was to come up with a way to tap into this great resource. They were able to accomplish this by repurposing existing genes to capture these six- and eight-legged snacks, and extract the nutrients found within them. Researchers who evaluated the digestive enzymes found in these plants noticed that there were quite a few similarities between these and defensive chemicals used by ancient flowering plants to protect themselves from pathogens and pests. Most carnivorous plants use similar enzymes including chitinases, proteases, and acid phosphatases (all of which have roles to play in the breakdown, dissolution, and absorption of nutrients from the corpses of their arthropod prey). In an interesting evolutionary twist, these chemicals were repurposed to eat some of the pests that they were originally protecting the plants from! How cool is that?!

If you want to learn more about the evolution of plant carnivory, I recommend reading the wonderful Smithsonian article linked in the resources below.

Carnivorous Plants and their Pollinators

With plants that have evolved to kill and consume arthropods, one can’t help but think about the pollinators that they depend on. How can plants attract both prey and pollinators? How do they go about selectively capturing the ones that they kill and extract nutrients from, while also protecting the ones that they rely on for pollination?

Insect and plant relationships can be multi-faceted, interesting, and extremely sophisticated (and plant/pollinator interactions are arguably some of the most interesting of these). Carnivorous plants have come up with ways to navigate this ‘pollinator-prey conflict’ utilizing a few main mechanisms. These include separation of the traps from the flowers, which is either done temporally or spatially. Some carnivorous plants will bloom before the traps have developed, allowing them to be successfully pollinated before they begin capturing prey, while other plants may physically separate the flowers from the traps themselves, often positioning flowers much higher than the traps which would be found closer to the ground (the method used by the Venus Fly Trap). They may also use different attractants (such as odors and colors) in their flowers and their traps to attract specific pollinators to flowers and only prey to traps; or they may use a combination of the aforementioned strategies.

The Venus fly trap protects its pollinators by spatially separating the flowers from the traps. Photo: NC Orchid, Wikimedia Commons https://commons.wikimedia.org/wiki/File:Dionaea_muscipula_in_flower_(16977455134).jpg

Growing Carnivorous Plants

Although many carnivorous plants can have complex growing requirements that can make them difficult to grow in captivity, there are quite a few plants that are well-suited to this. Furthermore, we all know some very ingenious gardeners that can grow some of the trickiest plants with ease, laughing in the face of what others may consider ‘impossible’! My mother is a classic example of one of these gardening goddesses who manages to propagate and grow some of the most ‘difficult’ plants, often the ones that I have told her will probably not be successful. To those of you who are like my mother, I salute you. For the rest of us, I will focus on some carnivorous plants that are more user-friendly.

There are a variety of carnivorous plants that grow well indoors, and several available resources to help troubleshoot growing requirements (including a variety of websites and blogs that are dedicated to carnivorous plants, some of which I have included in the resources below). For beginner-friendly carnivorous plants, I would recommend starting with Venus fly traps and sundews. Often far less fussy than most, these are sometimes considered ‘gateway’ plants for those who might be starting out on their carnivorous plant journey. Tropical pitcher plants (Nepenthes spp.) are another popular houseplant choice, and these vining beauties can be attractive additions to your carnivorous collection.

Tropical pitcher plants (*Nepenthes* spp.) are a popular choice for carnivorous houseplants. Photo: Abiya Saeed

There are also a few carnivorous plants that can grow well in outdoor gardens as long as the appropriate conditions are present. The purple pitcher plant (Sarracenia purpurea) is an example of a cold-hardy carnivorous plant that is especially suited to growing outdoors in North America (in USDA Plant Hardiness Zones 3-8), but there are also other temperate species of carnivorous plants that grow well in outdoor gardens in other temperate regions, and tropical carnivorous plants that are better suited to growing in more tropical regions. The most common carnivorous plants grown in outdoor gardens include temperate pitcher plants (Sarracenia spp.), sundews, and the Venus fly trap. I encourage you to look into the carnivorous plants of your region to see what could possibly grow in your home gardens. Note: you should never remove native plants from their native landscapes, because this could damage some of the fragile ecosystems in which they reside. Instead, source suitable plants from reputable suppliers who grow and propagate them sustainably.

Carnivorous plants for sale at a flower show. Photo: Abiya Saeed

Like any plant growing recommendations, there is never a one-size-fits-all approach to caring for carnivorous plants, nor are there plants that work well in every single situation. One of the keys to growing carnivorous plants is to make sure that you are providing these plants the right kind of growing conditions for them to thrive, often mimicking the conditions in which they thrive in nature. Most of these carnivorous plants need bright light, and supplemental lighting may be necessary if you don’t have a suitable location with access to enough sunlight. They also need lots of mineral-free water (many use distilled water for this), and nutrient-poor soils. You can even purchase carnivorous plant-specific soil mixes to simplify this process. Humidity is another consideration, and humidifiers, misting, or using terraria that can maintain humid conditions may be necessary. These plants don’t need to be fertilized, and it is important not to overfeed them. Indoor plants can be fed one or two insects per month (don’t feed them meat), whereas outdoor plants will probably not need to be intentionally fed, (as they can often get their insect nutrient sources on their own), but make sure they are grown in a location that has access to insect prey.

(If you are a carnivorous plant caretaker, what are some of your favorites to grow?)

More Information:

Carnivorous Plants (Penn State University):
https://extension.psu.edu/carnivorous-plants

How Carnivorous Plants Evolved:
https://www.smithsonianmag.com/science-nature/how-carnivorous-plants-evolved-180979697/

El-Sayed, A., Byers, J. & Suckling, D. Pollinator-prey conflicts in carnivorous plants: When flower and trap properties mean life or death. Sci Rep 6, 21065 (2016). https://doi.org/10.1038/srep21065

Some Resources for Growing Carnivorous Plants:

https://carnivorousplantnursery.com/blogs/cpn-blog

https://www.carnivorousplants.org

https://tomscarnivores.com/blog/start-here

The Dirty Truth Behind the “Dirty Dozen”

By: Abi Saeed

Pesticide residues and risk assessments have been a major topic of interest and inquiry for me for over a decade, and something that I wanted to write about on the Blog for quite some time. Over the past couple of months, I have had several inquiries from people regarding the “Dirty Dozen” list, so I thought this was the perfect time to organize the evidence-based data on this topic. To see a prior post on this topic, you should also check out Jeff Gillman’s post on the Dirty Dozen from 2010 and a follow up post from 2011.

Before diving too deeply, I wanted to acknowledge some of the articles and resources that I leaned heavily on while putting this post together. These include an excellent article by University of California Davis Extension Food Toxicologist Dr. Carl Winter on pesticidefacts.org, and an article authored by multiple experts from University of Arkansas Division of Agriculture Research & Extension (Dr. Amanda McWhirt, Dr. Jackie Lee, and Ples Spradley). Since both of these articles are over 5 years old, I have updated some of the information in my post to reflect any changes in the science and methodology since the time their articles were published. I also want to acknowledge that much of the regulatory information that I will be sharing within this post will pertain to agriculture in the United States, and for more detailed information on this topic pertaining to other countries, I strongly encourage you to seek out evidence-based resources and/or reach out to knowledgeable experts.

What is the ‘Dirty Dozen’

Aside from being a great World War II film from the late 1960’s, the term ‘Dirty Dozen’ also refers to a consumer-focused publication put together by an environmental advocacy group based in the United States. The Dirty Dozen is a list of 12 produce items (fruits and veggies) that allegedly contain the highest pesticide residue levels (dubbing them to be the ‘dirtiest’). This list is developed annually by the Environmental Working Group (EWG) with rankings that are based on United States Department of Agriculture’s (USDA) Pesticide Data Program (PDP) report. Although this sounds important and valuable to share with consumers, the information contained in these lists is derived through problematic methodology, disseminated using a lack of complete and evidence-based data, and results in unnecessary fear and uncertainty surrounding the consumption of fruits and vegetables that can have significant negative ramifications for growers and consumers alike.

The EWG’s “Shopper’s Guide to Pesticides in Produce” deters people from buying conventionally grown produce on the “Dirty Dozen” list, encouraging them to only purchase organic versions of these items. This annual guide also contains a “Clean Fifteen” list which includes produce items with the “lowest amounts of pesticide residues”. Neither list goes into detail regarding what these residues actually are, and whether they are even harmful to the consumer, and are therefore continually challenged by many scientists as lacking in scientific credibility.

The 2025 Dirty Dozen list is as follows:

Spinach
Strawberries
Kale, Collard, and Mustard Greens
Grapes
Peaches
Cherries
Nectarines
Pears
Apples
Blackberries
Blueberries
Potatoes

Recently harvested strawberries. Photo: **Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org**

EWG’s Dirty Dozen and Clean Fifteen methodology

Prior to 2025 EWG’s Dirty Dozen list was formulated primarily using percentages of samples with detectible pesticides and the number and amount of pesticides detected (with absolutely no information regarding the relative toxicity of these pesticides). As of this year, they have included the metric “overall toxicity of pesticides on a crop” as part of their screening criteria. Although this is a step in the right direction, it is still arguably incomplete information to share with consumers (especially since the most important component, whether these residue amounts are actually harmful to consumers, is still not addressed by any of their metrics, nor clearly communicated in their publications and marketing). This glaring omission is a big red flag in the credibility of this publication, and one of the main reasons why I have such a problem with it. As many of you avid Garden Professors Blog readers know from the many great science-based posts that have been shared (including Linda’s article on Recognizing Bad Science), we need to look carefully at the information being shared, regardless of the source, and make sure that it is evidence-based, credible, and complete.

Understanding Pesticide Safety

I want to caveat this section by stating that this is covering the science pertaining to pesticides and human health based on the research we have on this topic to date (which is subject to change as more evidence-based information comes to light). The scope of this Blog post does not cover environmental/ecological/economic/etc. impacts of pesticides in general nor the overarching impacts of various types of agriculture and food production systems (both of these are very complex topics which will require much more time and research to cover).

Although the term ‘pesticide’ is synonymously used with insecticides by many, pesticides are actually a broad category that includes all substances used to control or eliminate pests (including weeds, arthropods, vertebrate pests, pathogens, etc.). Therefore herbicides, insecticides, miticides, rodenticides, fungicides, bactericides, etc. all fall within the category of ‘pesticides’. Humans have been using ‘pesticides’ for thousands of years, though much of the innovation in pesticides (especially synthetic formulations) has occurred over the past 100 years. We have also greatly expanded our understanding and implementation of safety protocols and consideration for human and environmental health especially over the past 50 years (since Rachel Carson’s ‘Silent Spring’ and the formation of the U.S. Environmental Protection Agency (EPA) in 1970). Thankfully we have come a long way from the ‘DDT is good for ME-E-E’ era (and still have quite a long way to go). Although we are not perfect, pesticides in general are continuing to become safer and more effective, and products with higher toxicity and non-target effects are continually being phased out in support of better chemistries with fewer human health and environmental impacts (though the latter has much more knowledge gaps than the former, and we still have a LOT more work to do on this front). As we learn more about these products with scientific studies, we continue to update our protocols pertaining to them, though there are still knowledge gaps which continue to be explored by researchers. As Extension and IPM (Integrated Pest Management) professionals, we continue to educate people on the importance of pesticide safety, and urge people to think of the environmental impacts of these products, using them only after other IPM strategies (such as cultural, mechanical, and biological controls) have been unsuccessful. Anyone who uses pesticide products (whether Restricted Use Pesticides applied by Certified Pesticide Applicators and those under their direct supervision, or readily available general use pesticides such as Neem Oil, Insecticidal Soaps, etc.) should do so responsibly and in accordance with the label (the label is the LAW!), only when needed, and minimize negative environmental impacts when possible. The history of pesticides and formation of current regulatory protocols is a fascinating topic that I encourage all of you to read up on if you are interested (and may be an interesting topic for a Blog post in the future).

Home garden pesticides on a retail shelf from 1997. Photo: **Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org**

Now that we have covered pesticide basics, let’s get into pesticides and food safety in Organic and Conventional agriculture. First and foremost, if you are purchasing organic produce, that does not mean it is pesticide-free. In the United States, Certified Organic produce refers to food items that are grown utilizing a specific set of principles governed by the National Organic Program. Furthermore, there could be several conventional operations that still follow some of these principles, though may not be Certified Organic. An organic pesticide is basically a pesticide that is approved by the USDA for use in organic agriculture. Although pesticides used in organic agriculture are usually naturally derived, there are also synthetic pesticides that meet the criteria and are allowed in organic agriculture (just as there may be organic pesticides used in conventional agriculture). All pesticides utilized in the U.S. (with the exception of minimum risk pesticides) are registered with and regulated by the EPA. Any of the aforementioned pesticides that are used and sold within the U.S. have rigorous testing surrounding their safety for humans (and maximum allowable concentrations which are set at levels significantly below [10-1000 times lower] those that caused no adverse effects during testing), labeled according to these appropriate evidence-based safety guidelines, and off-label use is prohibited, routinely investigated, and enforced. Regardless of organic/conventional designation: just because something is naturally derived does not mean that it is safer than synthetically derived products. There are many natural substances that are extremely toxic (eg. Botulinum toxin, Ricin, Cyanide, Arsenic, Asbestos, etc.) and many synthetic ones that are relatively benign in comparison. In summary: Organic does not mean pesticide free, and natural/naturally derived does not mean safe.

For any of us that have taken a toxicology class, one of the most memorable take home messages was “The dose makes the poison”. Credited to a Swiss physician named Paracelsus in 1538, this statement applies to any chemicals (including water, salt, oxygen, caffeine, Aspirin, etc.) that are consumed or absorbed by us, forming the foundation of health and safety guidelines that determine the maximum allowable concentrations (tolerance levels) of these substances in our food, water, and the environment.

One of the most useful and illuminating courses I have ever taken in my career was Environmental Risk Assessment, which covered important topics including toxicology, pesticide risks, and invasive species (among other concepts). This course also detailed how Risk Assessments are conducted, the rigorous regulatory processes and evaluations required before products are even available for use, and the evidence-based tools used to determine whether a substance is hazardous and at what level (dose). A great summary of the Risk Analyses pertaining to pesticides and food safety have been summarized by Alejandro Fernández, Agronomist and Director of Hygiene and Safety of Products of Plant Origin SENASA (Argentine Food Safety and Quality Service), on the Pesticide Facts website (link in resources). These Risk Assessments and Analyses are the foundation of how we go about making determinations regarding any substances that we may be exposed to (including food and medicine).

The Issues with the ‘Dirty Dozen’

One of the biggest issues with the Dirty Dozen list is the fact that they do not communicate what having the highest (and lowest) pesticide residue levels even means. They do not conduct an accurate Risk Assessment to be able to support their message for avoiding conventional produce on this list. Although they do talk about the hazards (substances that have a potential to cause harm to us), they omit the crucial component of actual risk (likelihood of that substance causing harm to us), which incorporates another critical component of Risk Assessments: Exposure (how much of the hazard we are exposed to over a given period of time). If we looked at actual risk from the residues (incorporating hazard and exposure) we would find that the residues found on these produce items on the Dirty Dozen list are extremely low, and far below the threshold of having any risk associated with them, especially if we account for exposure (how many we consume on a daily basis, and over an extended period of time). A peer-reviewed Risk Assessment on pesticide residues published in the Journal of Toxicology by Winter and Katz (2011) in response to EWG’s 2010 Dirty Dozen list found just that (link in resources). Their conclusions were: (1) exposures to commonly detected pesticides in the 12 Dirty Dozen commodities had negligible risks for consumers, (2) substituting organic commodities for these conventionally grown ones did not result in any significant reduction of risk, (3) the EWG methodology for determining risk of these 12 products lacks scientific credibility (Winter and Katz, 2011).

Based on this cool pesticide residue calculator (link in resources), a woman of average height and weight could consume 774 servings of spinach or 453 servings of strawberries (the #1 and #2 produce items on the Dirty Dozen list) in a day without any effects. This calculator utilizes the highest possible amount of pesticide residue recorded by the USDA in these produce items, and not the average amount. Now I don’t know about you, but I would personally struggle to consume even 10 cups of strawberries in a day (every day), let alone over 450 cups. This is a great illustration of how dose/risk works, and why these produce items are considered safe for human consumption in conventional agriculture.

Pesticide residue calculator results. https://www.safefruitsandveggies.com/pesticide-residue-calculator/

In summary: the EWG fails to mention that these residue levels are still safe, and far below the thresholds that can begin to have an impact on the consumer. This can have negative ramifications for farmers that grow the produce on these lists, especially if they grow conventionally as opposed to organically. Concerns that people may opt to avoid conventionally grown produce, or avoid those specific produce items altogether is an added hurdle for growers to worry about. Both conventional and organic farmers care about what they produce, and also want our food to be safe (for their families and ours). Our regulatory processes further monitor this safety in both conventional and organic production systems, and as the science is updated, so are these processes. Although many lack access to this, if you have access: reach out to local growers and get to know what their practices are to get a better understanding, and support local farmers when possible.

Furthermore, marketing and messaging like EWG’s Dirty Dozen list discourages people from consuming certain produce, and with only 1 in 10 Americans eating enough fruits and vegetables in their diet, the cons far outweigh the pros for this messaging. An article from the Alliance of Food and Farming details some of these negative impacts (see Resources). This type of fear-mongering disproportionately impacts consumers in lower income brackets, and those that lack access to certain produce. A 2016 consumer survey showed 15% of lower income shoppers surveyed would opt to eat less fruits and vegetables after hearing about the ‘Dirty Dozen’ (Huang et al., 2016).

The take home message should be: the produce that you purchase, whether conventional or organic, is safe to be consumed (and backed by rigorous testing that determines this). Do not be deterred from eating the produce of your choice. Choose produce that is enjoyable, affordable, and accessible to you. And whether conventional, organic, or home-grown: eat more fruits and veggies!

Delicious strawberries. Photo: **Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org**

Resources:

Pesticide Facts: ‘Dirty Dozen’ List Contaminated with Non-Science:
https://pesticidefacts.org/perspectives/dirty-dozen-list-contaminated-with-non-science/

What is the “Dirty Dozen” list and should you be worried about it:
https://www.uaex.uada.edu/farm-ranch/crops-commercial-horticulture/horticulture/ar-fruit-veg-nut-update-blog/posts/dirtydozen.aspx

Organic vs. Conventional Pesticides:
https://www.pubs.ext.vt.edu/ENTO/ENTO-384/ENTO-384.html

Pesticide Facts: Pesticide Risk Analysis Ensures Food Safety:
https://pesticidefacts.org/perspectives/risk-analysis-ensures-food-safety/

USDA PDP Report (2024):
https://www.ams.usda.gov/sites/default/files/media/PDPLABOPSOP.pdf

Pesticide Residue Calculator:
https://www.safefruitsandveggies.com/pesticide-residue-calculator/

Alliance for Food and Farming: Consumer Impacts
https://foodandfarming.info/alliance-for-food-and-farming-dirty-dozen-list-scientifically-unsupportable-hurts-consumers/

Washing fresh fruits and vegetables safely:
https://extension.umn.edu/preserving-and-preparing/wash-fresh-fruits-and-vegetables

Carl K. Winter and Josh M. Katz, 2011. Dietary exposure to pesticide residues from commodities alleged to contain the highest contamination levels. Journal of Toxicology, Article ID 589674, doi:10.1155/2011/589674.
https://pmc.ncbi.nlm.nih.gov/articles/PMC3135239/

Yancui Huang, Indika Edirisinghe, and Britt M. Burton-Freeman, 2016. Low-income shoppers and fruit and vegetables: What do they think? Nutrition Today 51(5): 242-250.
https://journals.lww.com/nutritiontodayonline/fulltext/2016/09000/low_income_shoppers_and_fruit_and_vegetables__what.6.aspx

An Ode to the Dandelion:

Deciphering fact from fiction for one of the most infamous plants in the world.

Dandelions can be a bit of a polarizing subject for gardeners. Some absolutely love them, while others may despise seeing these bright yellow bursts of unconformity in an otherwise ‘pristine’ lawn and garden landscape. Many often find themselves somewhere in the middle of this spectrum. Dandelions are also used as a symbol for resilience–growing despite all odds in some very harsh and unforgiving environments–often ones where few cultivated plants would successfully grow. Some people enjoy eating them, while others embrace them as a source of nectar, pollen, and food for other critters in the landscape. There is a lot of wonder in the way that they disperse, and many kids and adults alike have enjoyed blowing on dandelion seed heads (with or without making a wish) to watch them float away in the wind, drifting to new locations that they can conquer as their own. There is even an annual festival devoted to dandelions in Carbondale, Colorado (located in the same county where I served as an Extension Agent several years ago). When I attended years ago, it was such a cute and unique event, where people were wearing dandelion flower crowns, sharing art and artisan products associated with dandelions, and enjoying music and merriment in the spirit of the whimsical yellow plant. There is a lot of myth, magic, and majesty associated with dandelions, that it can be hard to decipher fact from fiction.

I get asked about dandelions more than any other plant combined– especially pertaining to pollinators, but also many other things. These queries come from people of all backgrounds and viewpoints, ranging from: how to get rid of them, to: how one can encourage and/or intentionally grow and cultivate them. These queries are especially common as spring rolls into Montana with the classic yellow bursts of color being some of the most visible flowers at this time of year, especially in the colder climates of zone 4 in the greater Rocky Mountain region. I have found myself endlessly poring over research to try and answer some of those questions, that I thought it would be fun to ‘dig in’ (pun always intended) to the lore of dandelions and the science-based information that we have on this notorious plant.

The Dandelion

Dandelions (Genus: Taraxacum) are a widespread genus in the Aster family that can be found in most parts of the world, either as a native plant or naturalized through intentional and unintentional introductions. Although there are around 250 species in the genus, the most widespread dandelion species is Taraxicum officinale, also known as the ‘common dandelion’, which originates from Eurasia but is now naturalized in many parts of the world (and can be found on on every continent except Antarctica). For the purposes of this Blog post, I will be focusing on information pertaining to the common dandelion (Taraxicum officinale). This is considered a short-lived perennial plant that can reproduce sexually (through seeds) and asexually (through the roots), can withstand a wide variety of climates and soil conditions, all of which can contribute to the fact that dandelions are so prolific and widespread.

Dandelion seed head. Photo: **Joseph OBrien, USDA Forest Service, Bugwood.org**

Starting out as a rosette of lance-shaped leaves, it shoots up the characteristic yellow flowers in early spring. Each ‘flower’ is actually an inflorescence that consists of several ray and disc florets clustered together (similar to its relative: the sunflower). The length of the flower stalk is extremely variable, ranging from a couple of inches (in frequently mowed areas such as lawns) to multiple feet in length. I once saw a dandelion curiously poking out through the top of a boxwood shrub that was nearly 3 feet tall, and upon investigation, measured the stalk at a staggering 35 inches (which is half the length of the tallest dandelion stalk on record found in Ontario, Canada). The flowers are followed by the very distinct seed-heads which contain individual seeds, each of which are attached to a fine tuft of hairs (a pappus) that act as a parachute to aid in wind dispersal. Dandelions are well-known for their tap-root which can contribute to the plant’s drought tolerance, and allows them to compete well with other vegetation for limited resources.

Dandelion seed pappus. Photo: **Joseph Berger, Bugwood.org**

Dandelions as an Edible Plant

The fact that dandelions are edible is not a topic that is frequently debated. Many know this to be true. Almost every part of the common dandelion from the taproot to the flower heads is all edible (with the exception being the stems which contain a milky latex that can be very bitter). Plenty of dandelion recipes can be found with a quick Google search. There is, however, much debate about their taste. To some, dandelions are a whimsical treat, where you may enjoy the flowers or young leaves in a salad, while others choose to steep parts of the plant to make teas, or enjoy the fermented products as delectable dandelion wines. Furthermore, dandelions can be found in many skincare products, salves, lotions, herbal remedies, and more.

In North America, European settlers intentionally brought dandelions for their nutritional and medicinal value. They were intentionally grown alongside vegetable and herb plantings, and used to remedy a variety of ailments. The nutritious properties of dandelions are comparable to salad greens such as spinach and arugula. Leaves are high in potassium, calcium, and iron, whereas the roots can have diuretic and laxative properties. For more information on dandelions as food, check out the link to the publication from University of Wisconsin in the resources.

Dandelion Salad. Photo: University of Wisconsin-Madison Extension.

Although I have yet to find a dandelion recipe that I thoroughly enjoy (besides recipes that try and mask the flavors using in intense array of herbs and spices, or baking them into treats, brewing them into teas, and fermenting them into wines). I am not personally a fan of the bitter and earthy flavor of the raw plant, though I admit, I haven’t tried all variations of cooking or flavoring the parts of a dandelion. If you have a recipe you love and swear by, feel free to share it with me, and I will give it a try (as long as it isn’t too time and resource intensive). Regardless of your taste preferences, if you do choose to eat dandelions, collect them from a safe location, make sure that they have not been treated with any chemicals, and wash them thoroughly to remove any soil, debris, or insects.

Dandelions and Pollinators

Many embrace dandelions because of the associated value to pollinators. The science behind this, however, is not as black and white as some may think. Although dandelions can be convenient sources of pollen and nectar for pollinators in highly urbanized landscapes, especially early in the season when very few other plants may be flowering in some of these densely populated areas, they are not the highest quality source of food for many of our pollinators. Some claim that dandelions are the earliest flowering plants blooming in the spring, which is also untrue in many parts of the world. That being said, dandelions are among the most widespread and consistent sources of nectar and pollen in some landscapes (such as urban areas with fewer flowering plants intentionally incorporated to support pollinators all season long) and also some of the earliest blooming plants visible in these types of landscapes.

An Andrenid bee foraging on a dandelion. Photo: **B. Merle Shepard, Clemson University, Bugwood.org**

A lot of research has been done that shows dandelions attract a wide array of pollinator species, and can therefore be a critical source of food for pollinators in urban areas, where these plants are widespread and can act to bridge the gaps between other areas of more diverse floral resources (Larson et al., 2014). Research also shows that dandelions do not have the most nutritious nectar and pollen, lacking in certain important amino acids, making pollinators (such as honey bees) unable to survive on dandelions alone (Loper and Cohen, 1987). We also know that a dandelion-only diet can impact the ability of honey bees to rear brood (Herbert et al., 1970). Unfortunately, our research is usually restricted to managed bee species such as honey bees, so we have far less information on how most of our pollinator species (including the rest of our 20,000 species of bees) would respond to a dandelion-focused diet. What we do know is that pollinators need a varied diet with floral resources available all season long, including early and late in the growing season when some nectar and pollen collecting species have to begin provisioning their nests and when some species are getting ready to overwinter. Although there are countless flowering plants that are better for supporting pollinators, dandelions will always have a place on that list until more intentional pollinator-friendly plantings are incorporated.

Dandelions can also support caterpillars of a variety of butterfly and moth species. These caterpillars will use the rosette of leaves produced by dandelions as their primary source of food, or as part of a wider diet consisting of a variety of plants. These caterpillars, in turn, can be an important source of food for animals higher up on the food chain (including birds). This can make dandelions important for ecosystems beyond just their nectar and pollen for pollinators.

Dandelions as a Weed

Common dandelions are undoubtedly a resilient plant in many landscapes, as all of us have seen them popping up in lawns, through dense vegetation, in gravel roads and driveways, sidewalks, roadsides, and so on. In fact, it would be difficult to imagine a landscape without dandelions. Because they can grow in conditions that may not favor some other cultivated plants, and therefore may be found taking over areas where you wanted to grow something else, they are commonly considered a weed. In fact, they are probably the most famous weed you can think of, and the poster plant for many lawn care companies, herbicides, and other garden products aimed at controlling or limiting their abundance in our managed landscapes.

Some research shows that dandelions can compete with native vegetation for resources. Research in Japan on native Taraxacum spp. and the impact of growing alongside Taraxicum officinale showed a reduction in seed production for the native species (Kandori et al., 2009). The authors hypothesized that the more attractive flowers of T. officinale may deprive the native species of pollinators, resulting in a reduction of pollination services. They also stated that the transfer of pollen from the non-native species could interfere with the successful reproduction of the native species, however, this was disproven by hand-pollination experiments (Kyogoku, 2021).

In many home garden settings, whether or not something is a weed, is usually very subjective and dandelions are no exception. I, personally, don’t mind dandelions growing opportunistically in certain managed landscapes (though seeing non-native dandelions in natural ecosystems is an entirely different story). My stance on many persistent (non-noxious) weeds in the garden is usually a variation of ‘may the best plant win’, but I know that not everyone feels this way. Although some embrace the odd dandelion speckled in a lawn, when you have large swaths of dandelions in the place of what used to be turfgrass, the problem usually extends beyond dandelions themselves.

Dandelions aplenty! Photo: **Steve Dewey, Utah State University, Bugwood.org**

One of the best ways to combat dandelions in a turf lawn setting, is to make sure that your turfgrass is healthy and able to form dense coverage on the soil. Healthy turf can often outcompete weedy vegetation that can opportunistically take advantage of open spaces for establishment. Addressing soil compaction, nutrient needs, and responsibly caring for your turf lawns can all play a role in reducing weed issues, including dandelions. For situations where competing vegetation may not be an option, mulches can be used to reduce the presence of dandelions that may be found in flower beds or veggie gardens. Mechanical removal is also very effective for controlling dandelions, depending on the scale of the issue. Using your favorite tap-root removal tool (such as the aptly named dandelion fork) can remove plants without too much exertion. Pulling out as much of the root as possible will offer the best control, as dandelions are less likely to propagate from smaller root fragments.

Several herbicide options are also available for dandelion control. Broadleaf herbicides such as 2,4-D, dicamba, and MCPP (commonly found in ‘weed and feed’ fertilizer products) can be effective for dandelion control in lawn settings. Spot-treating individual plants using an appropriately labeled broadleaf weed killer is usually more effective than broadcast application across larger areas. Herbicides with the active ingredient Glyphosate are not as effective for long-term control of perennial weeds like dandelions, because they often knock back leaves without killing the roots, which allows the plants to regenerate. These products can be more effective if a plant is cut or mowed and the herbicide is carefully painted on the fresh cut, which can facilitate movement into the root system. Late summer and early fall is the best time to control perennial weeds such as dandelions. This is because these plants are moving resources from the foliage to the root system in order to prepare for winter, which can also help to transport systemic herbicides to their roots and/or deplete their root systems of energy for more effective and longer-lasting control. (Remember that herbicides may kill desirable plants, and not just weeds- so use them responsibly and sparingly while taking precautions not to apply them near susceptible plants). Always, always, always read and follow label directions, and if unsure: reach out to your Extension resources for assistance.

Make a wish! Photo: **Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org**

Whether you are a big fan of dandelions, or the opposite of that–I hope that you learned something new from this post–and continue to be curious about the plants that surround us!

Resources:

University of Wisconsin: Dandelion, Taraxacum officinale

Dandelion recipes: https://www.theprairiehomestead.com/2014/04/dandelion-recipes.html

Larson, J. L., Kesheimer, A. J., & Potter, D. A. (2014). Pollinator assemblages on dandelions and white clover in urban and suburban lawns. Journal of Insect Conservation, 18, 863-873. https://link.springer.com/article/10.1007/s10841-014-9694-9

Loper, G. M., & Cohen, A. C. (1987). Amino acid content of dandelion pollen, a honey bee (Hymenoptera: Apidae) nutritional evaluation. Journal of Economic Entomology, 80(1), 14-17. https://academic.oup.com/jee/article-abstract/80/1/14/757976?redirectedFrom=fulltext

Herbert, E. W., Bickley, W. E., & Shimanuki, H. (1970). The brood-rearing capability of caged honey bees fed dandelion and mixed pollen diets. Journal of Economic Entomology, 63(1), 215-218. https://academic.oup.com/jee/article-abstract/63/1/215/798721

Kandori, I., Hirao, T., Matsunaga, S., & Kurosaki, T. (2009). An invasive dandelion unilaterally reduces the reproduction of a native congener through competition for pollination. Oecologia, 159, 559-569.
https://link.springer.com/article/10.1007/s00442-008-1250-4

Kyogoku, D. (2021). Pollination from invasive dandelions is unlikely to reduce seed production in the native Japanese dandelion, Taraxacum japonicum. Weed Research, 61(2), 106-114.
https://onlinelibrary.wiley.com/doi/pdf/10.1111/wre.12462?casa_token=6TlTr9JK5KkAAAAA%3AkxZ20v6UZKUGMCYpexHDgwO4DVrRZy2Ilc2q6u_bHPAFuysDEjDaXZ0gETfo2FQvV4w_7p_iyUsabFQE

8 Legged Friends: Spiders in the Garden

Even though some may not be fond of them, we understand that most spiders are beneficial, excellent predators of arthropod pests and are extremely interesting organisms. Gardeners are often really enthusiastic about this group of arthropods and enjoy observing them in outdoor landscapes, usually at a comfortable distance. There are some of us who enjoy the company of these creatures in closer proximity, even indoors and as pets (myself included).

Jumping spider with prey.
Photo: **David Cappaert, Bugwood.org**

Writing a post about spiders has long been on the back of my mind, and a topic that has been requested multiple times. So as I sit in front of my fireplace on this snowy Montana evening, thinking back to the several spiderwebs speckled in between my wood pile, I thought that this month would be the perfect time to do some spider research. For this post I will be focusing on the outdoor spiders that we can commonly find in our gardens: who they are, what they do, and how we can make more of a hospitable environment for them. As usual I will caveat this by saying spiders are a broad group, and since I can’t exhaustively cover them in the scope of this post I will share resources for you to learn more at the end.

Types of Spiders in the Garden

Spiders are arachnids (class: Arachnida) and share this category with scorpions, ticks, and mites. They fall within the order Araneae, containing more than 50,000 species across 134 different families, making them the largest group of arachnids in terms of species diversity. They have 2 body segments, 8 legs, chelicerae with fangs, and spinnerets that can produce silk. Although all spiders can produce silk, not all of them make webs. Nearly all spiders are venomous (except for 2 families which lack venom glands) however, most spiders either do not bite humans, do not have venom potent enough to negatively impact us, or fangs capable of penetrating our skin. Spider venom is primarily used to immobilize and subdue their prey which are often smaller arthropods like insects. There are a few spiders of medical importance (as we know) who can be found in close proximity to humans, and some people can have an allergic reaction to spider venom (like with many insect venoms). Most spiders are carnivorous, feeding on small arthropod prey, and some of them supplement their diet with plant products like nectar and pollen. One species (Bagheera kiplingi) is known to be primarily herbivorous. For the most part though, spiders are amazing generalist predators most of which are not dangerous to humans and all of which will not seek you out and hunt you down (despite what some exaggerated spider-related media and tropes may claim).

Jumping Spiders

Arguably the cutest group of spiders around, jumping spiders (family: Salticidae) can sometimes even convince the most spider averse people to take a second look in appreciation. Jumping spiders comprise the largest family of spiders, containing more than 6000 species worldwide. These often brightly colored critters with distinctly large eyes do not spin webs, but actively hunt prey, often during the daytime with their excellent vision. Aptly named for the large leaps they can make while hunting for prey or escaping threats, they can be extremely entertaining to watch around the garden. They can use their silk to make small insulated shelters under leaves, bark, or between rock cracks. They also produce compounds like glycol and other proteins which act like an antifreeze, allowing some of them to remain active in colder and even freezing temperatures.

Jumping Spider, arguably one of the cutest arthropods of all time!
Photo: **Joseph Berger, Bugwood.org**

Orb-Weavers

The characteristic mascot of spiders in the garden, orb-weavers (family: Araneidae) build the very familiar large, circular spider webs that we all can easily picture. These magnificent builders lay in wait of prey that flies or crawls onto the sticky parts of their webs. After biting their prey to immobilize it, they proceed to wrap them in silk. Most of them are active at dusk and will rebuild their webs each day.

Yellow Garden Spider (*Argiope aurantia*).
Photo: **Leslie J. Mehrhoff, University of Connecticut, Bugwood.org**

Wolf Spiders

Wolf spiders (family: Lycosidae) are another group of non-web spinning spiders known for their active hunting abilities. Some will wander around the ground, searching for prey, while others wait in burrows for an unsuspecting victim to walk by. These hairy grey, black, and brown spiders have excellent eyesight and many of them are primarily nocturnal hunters. Females lay their eggs in a silk sac and actively protect them by carrying them around. Once they hatch, the mother will carry these spiderlings (in some cases, over 100 of them) on her back, which is quite a spectacular sight to behold.

A wolf spider mom with her newly hatched spiderlings on her abdomen.
Photo: **Joseph Berger, Bugwood.org**

Ground Spiders

Ground spiders (family: Gnaphosidae), similar to wolf spiders, are nocturnal hunters who use their quick speed to hunt down and chase after prey. They use their sticky silk to entangle their prey, immobilizing them. This hunting behavior allows this group of spiders to target prey larger in size than themselves. During the day they can be found in silk shelters. A really cool group in this family includes the ant-mimicking ground spiders (genus: Micaria). The first time I spotted this spider under a rock in Kentucky, all of my entomological instincts were telling me that it doesn’t quite look like an ant. Upon closer observation, the 8-legs gave it away (but not before our whole group was thoroughly impressed by its ant-like appearance).

Ant mimicking spider (genus: *Micaria*). Photo: Abiya Saeed

Crab Spiders

These sometimes brightly colored and distinctly shaped spiders (family: Thomisidae) can also be found worldwide. They are called crab spiders because of the way that their two pairs of front legs (which are longer than the rest of their legs) are positioned, in addition to their sideways and backwards movement which can be crab-like. These are another group of non-web making spiders which act as ambush predators. Sometimes referred to as “flower spiders”, they can be found perched on a flower, waiting for a visitor to stop by for some nectar before they pounce.

A well-camouflaged crab spider, waiting to ambush a flower visitor.
Photo: **Keren Levy, Bugwood.org**

Lynx Spiders

Lynx spiders (family: Oxyopidae) are another group of ambush hunters that target prey species found on plants. Similar to crab spiders, some species can also capture pollinators while they patiently await them on flowers. Due to their often green and brown coloration, they can camouflage themselves in plants, making hunting for prey easier. Species in this group are also known to be important for biocontrol in agricultural systems.

A green lynx spider (*Peucetia viridans*) with prey.
Photo: **Joe Culin, Clemson University, Bugwood.org**

Funnel-Weavers & Grass Spiders

Funnel-weavers (family: Agelenidae) are another cosmopolitan group of spiders known for their very quick speeds and their unique webs. Named for the structure of their webs, which looks like a flat sheet that tapers into a funnel-shape, these spiders lay in wait for prey that walk across these sheets, triggering vibrations that cause the spider to ambush them. Although these webs are not sticky (unlike sections of orb-weaver webs), they do contain a lot of silk fibers that can entangle their prey. Once the prey have been subdued by a quick bite, the funnel-weaver grabs their tasty meal and retreats back into the safety of its funnel. Not to be confused with funnel-web tarantulas, these spiders can create their funnel-shaped webs in leaflitter, on soil, or in grass. This family includes grass spiders and also the common house spiders. Some species may seek refuge indoors during the winter time (an example being Hobo spiders), which can sometimes be a nuisance for people.

A funnel weaver web in a Taxus shrub.
Photo: **Whitney Cranshaw, Colorado State University, Bugwood.org**

Sheet Weavers

Sheet weavers or money spiders (family: Linyphiidae) are a group of very tiny spiders, containing over 4700 species worldwide (making them the second largest family after jumping spiders). Although they are very widespread, their small size makes them easy to miss. Many species of Lyniphiids are considered excellent biocontrols of small soft-bodied arthropod pests such as aphids.

Harvestmen

Although Harvestmen (Order: Opiliones) may greatly resemble them, they actually aren’t spiders, even though they are arachnids. They do have 8 legs, but only have one body segment, no fangs or venom glands, and do not produce any silk. They are sometimes referred to as daddy-longlegs, not to be confused with daddy-longlegs spiders, which are in fact spiders in the family Pholcidae. There are many tall tales associated with this group of spiders so to learn more about them check out the resources. Harvestmen prefer moist environments such as caves, leaflitter, and under logs. They are omnivores and opportunistically feed on decaying vegetation, carrion, animal waste, and small arthropods. They can also aggregate together to retain moisture (which can be quite a sight to behold).

Benefits of Spiders

Due to their carnivorous diets, diverse hunting behaviors, and widespread distributions, spiders are excellent beneficial organisms which can reduce pest populations in a wide variety of landscapes. They are also well-known as naturally-occurring biological controls in many agricultural and horticultural systems. Several studies have been conducted which demonstrate the benefit of a variety of groups of spiders in these systems. Spiders can reduce populations of common groups of pests including caterpillars, aphids, leafhoppers, planthoppers, and beetles.

Many groups of spiders can be found in agricultural systems. An analysis by Young and Edwards (1990) demonstrated the presence of over 600 spider species spanning 26 families found in 9 specific field crops in the United States. According to their analysis: 5 spider families comprised the majority found in field crops including Salticidae [jumping siders], Linyphiidae [sheet weavers], Araneidae [orb-weavers], Theridiidae [tangle-web spiders], and Lycosidae [wolf spiders] (Young and Edwards, 1990). A study conducted by Akhtar et al. (2024) showed 45 spider species spanning 13 families in maize crops in the Punjab region of Pakistan. The families that made up the majority of these species included Araneidae [orb-weavers], Lycosidae [wolf spiders], and Salticidae [jumping spiders] (Akhtar et al., 2024). These are just a couple of examples of studies that have been conducted, though there are many more you can find!

An orb-weaver with grasshopper prey.
Photo: **Ronald F. Billings, Texas A&M Forest Service, Bugwood.org**

Several studies have also demonstrated that presence and density of spider populations resulted in an increase or improvement in crop production. A meta-analysis conducted by Michalko et al. (2019) evaluated 58 studies conducted on the impact of spider density on crop performance and found an overall positive result. Agricultural pest insects were suppressed in situations of higher spider density in 79% of cases. Their efficacy in biocontrol varied depending on the type of crop, but was highest in rice, grape, cabbage, and wheat systems (Michalko et al., 2019).

As more research continues to be conducted, I am sure that we will find many more instances in which spiders improve crop productivity through the suppression of common pests.

Protecting and Conserving Them

All of these studies show that the presence of beneficial organisms like natural enemies can be important natural biological controls which can assist us in having a more productive garden (whether the scale of production is large or small). As such, thinking about protecting and conserving these awesome generalist predators is in our best interest.

Implementing practices that can reduce negative impacts on spiders, and creating a landscape that favors them can have wonderful benefits for our gardens. Much of this can also be intuitively considered when you think about the biology and hunting behavior of these groups of spiders. A study conducted by Mashavakure et al. (2019) on the impact of farming practices on spiders in southern Africa showed a variety of common trends which can be adapted for gardens of different scales. In this study, they showed that the two factors that had the largest impact on spider populations were tillage and mulching (Mashavakure et al., 2019). Practices with minimum tillage had highest populations of Lycosidae [wolf spiders], Gnaphosidae [ground spiders], and Salticidae [jumping spiders] (Mashavakure et al., 2019). Plots that had the lowest mulching levels also had the highest populations of Gnaphosidae [ground spiders] and Thomisidae [crab spiders] (Mashavakure et al., 2019).

Structural complexity and diversity of vegetation is another way that you can conserve and increase beneficials in the landscape (including spiders). Having a variety of plants of different sizes and maintaining this habitat year-round can provide shelter, hunting spaces, and overwintering sites for spiders in the home landscape. In addition, reducing practices that can harm beneficials including practicing IPM and reducing the use of broad spectrum insecticides, also goes hand in hand with creating more habitat for spiders.

A crab spider (*Misumenoides formosipes*) on a flower.
Photo: **David Cappaert, Bugwood.org**

I hope this post illuminated some of the diversity and beauty of our favorite 8-legged garden companions. Even if some may not want to snuggle up to them, we as gardeners can always appreciate the importance of these amazing creatures in our landscapes.

Resources:

Daddy-longlegs myths: https://spiders.ucr.edu/daddy-long-legs

Overview of Spiders in Agriculture: https://vegcropshotline.org/article/insect-spotlight-spiders-an-overview-of-their-role-in-agricultural-systems/

Young, O. P., & Edwards, G. B. (1990). Spiders in United States field crops and their potential effect on crop pests. Journal of Arachnology, 1-27.
https://www.researchgate.net/profile/G-Edwards/publication/256082787_Spiders_in_United_States_field_crops_and_their_potential_effect_on_crop_pests/links/00463539065408dc43000000/Spiders-in-United-States-field-crops-and-their-potential-effect-on-crop-pests.pdf

Akhtar, N., Tahir, H. M., Ali, A., Ahsan, M. M., & Abdin, Z. U. (2024). Assessment of Biodiversity and Seasonal Dynamics of Spiders in Maize Crops of Punjab, Pakistan. Journal of Asia-Pacific Biodiversity.
https://www.sciencedirect.com/science/article/pii/S2287884X2400061X

Mashavakure, N., Mashingaidze, A. B., Musundire, R., Nhamo, N., Gandiwa, E., Thierfelder, C., & Muposhi, V. K. (2019). Spider community shift in response to farming practices in a sub-humid agroecosystem of southern Africa. Agriculture, Ecosystems & Environment, 272, 237-245.
https://www.sciencedirect.com/science/article/pii/S0167880918304821

Ants in my Plants!

Ants are a very familiar and recognizable group of insects in our homes and gardens. Due to their common presence on or around our plants and garden pests, some people consider that they may be the cause of some of the issues that we see. For the most part, ants play important and diverse roles in their ecosystems and are usually beneficial to us in our garden settings. As with every situation, however, there are always exceptions.

Ants are in the family Formicidae, within the order Hymenoptera (making them relatives to bees and wasps). They are also eusocial, meaning that they share characteristic traits including a queen (though some species have multiple queens that peacefully share a nest) taking care of brood cooperatively (usually through workers), and reproductive division of labor (meaning that certain groups within a species play a role in reproduction while others do not). Eusocial insects are able to collect a large array of resources, store/share them within their colonies, and can have interesting and complex methods of communication through pheromones. Other eusocial insect groups include bees, wasps, and termites- though there are more eusocial ant species than all of these other groups combined with an estimated 12-20,000 species (and likely even more that are undescribed).

Ants also have very interesting and elaborate communication, movement, and mating behaviors. They send individuals to scout out ideal sources of food and nesting areas, and then use trail pheromones to navigate their way to these locations. When the mating season arrives, winged male and virgin female ants take nuptial flights and then go on to start new colonies. These newly mated queens store the sperm from these nuptial flights and will use these stores to selectively fertilize her eggs for the duration of her life.

Ants are omnivores, and feed on a variety of organic materials including fungi, nectar, seeds, plants, arthropods and other small animals (acting as predators or scavengers). Even though they do sometimes feed on plants, they rarely do enough physical damage to be very noticeable in most situations. With the exception being species of leafcutter ants (primarily found in tropical climates such as central and South America). These ants form complex societies and even farm their food. Like their name suggests, they cut leaves off plants and take them back to their large underground nests in which they cultivate and feed on the fungus that grows on these chewed leaves. They can take a significant amount of vegetation to accomplish this task, though plants often easily recover by producing new leafy vegetation. In temperate climates, we don’t need to worry about these ant species ruining our favorite ornamental tree or shrub.

Leafcutter ants (*Acromyrmex* sp.) moving leaves to their nest.
Photo: **Whitney Cranshaw, Colorado State University, Bugwood.org**

There are also several ant species found in lots of different climates, which can be nuisance pests due to their nesting habits, behaviors and/or close proximity to humans – but I will not be discussing these ants in this post. The goal of this blog post is to discuss examples of common ants that can be found in our yards and gardens and what they might be up to. The Ants in our Plants, so to speak.

Ants as Beneficial Garden Guests

Many ants are great generalist predators, especially when they work together! In fact, one of my first memorable entomological observations was a large white grub (the larva of a Scarab beetle) in my family’s lawn in Pakistan being swarmed by 40-50 ants that were working together to take down this sizeable opponent. I was 7 years old at the time, but I recall being endlessly fascinated by what I saw, and continued to observe the epic battle for nearly an hour.

Ants feeding on white grub (Scarab beetle larva).
Photo: **Alton N. Sparks, Jr., University of Georgia, Bugwood.org**

If a large grub (or even slightly larger animals) didn’t stand much of a chance against a determined colony of ants, smaller soft-bodied arthropods would likely be no match! In fact, ants have been recognized as great biological control agents in agriculture, especially in tropical climates. That being said, they can also have a few behaviors that can make them detrimental to our agricultural (and garden) productivity, as I will explain in the next section.

Ants as companions to other insects

In some situations ants can act in a way that is contrary to our gardening goals by supporting, protecting, and partnering with other common pest insects. These are often referred to as ‘symbiotic relationships’ (where these organisms have a close association with one another, that may benefit one or both of these groups). You may be familiar with some of these associations, which often involve a honeydew producing insect (such as an aphid or a scale insect) being closely guarded and “farmed” by a group of ants.

*Lasius* ants tending to their honeydew-filled mealybug “herd”. Photo: Abiya Saeed

The reason that several ant species associate with these honeydew producing insects is due to the fact that their waste (a sugary substance that is excreted from a diet rich in plant sugars referred to as honeydew) is an excellent nutrient rich food source. These ants will often “milk” these sap-sucking insects by manipulating their abdomens with their antennae in order to coax out more honeydew. Having such a great source of food in such close proximity also gives the ants an incentive to protect it – which means that these honeydew producing insects basically have ant bodyguards that can defend them from natural enemies (such as generalist predators and parasitoids). In some cases, ants will herd or move these sap-sucking insects to juicier plant tissues, and to safer locations. When these ants move to a new nesting site, they will bring aphid eggs with them in order to establish a new “herd”.

*Lasius* relocating some of their honeydew filled mealybugs to a new location.
Photo: Abiya Saeed

Seeing this in action can be quite a sight to behold. In fact, if you are seeing ants grouping around some of your garden plants in larger quantities, take a look to see if you can spot some of these honeydew producing pests as well.

This symbiotic relationship between ants and honeydew producing pests can also have significant economic and ecosystem impacts! As a meta-analysis by Anjos et al. (2022) demonstrated that although ants in various cropping systems can reduce the abundance of non-honeydew producing pests, their impact on honeydew-producing pests is reversed! This analysis showed a variety of instances in which ants decreased the number of natural enemies, and increase the abundance of these honeydew-producing pests (Anjos et al., 2022).

Ants in turfgrass

Since many ant species nest in complex underground colonies, they can move large portions of soil in order to create these dynamic living spaces. Ant nest mounds in locations where we don’t want to see them can often be a nuisance to us, and sometimes even detrimental to our plants. I receive calls about this in a turfgrass setting (especially if the turf isn’t very dense or competitive), where your plants are mowed low enough to make even smaller nests noticeable. Even though these ants feed on a variety of common turf pests like white grubs and cutworms, their nests can sometimes be unsightly. Although this usually isn’t a problem in home gardens (and raking small mounds, using a hose, and increasing your mowing height can be simple fixes which could cause the ants to relocate), in situations like golf courses where low mowing heights are an important component of play mechanics, this can be more of a problem.

Ant mound in turfgrass.
Photo: Dan Potter, University of Kentucky

As you would expect, larger ant nests that happen to be built in your home gardens can be an even larger problem, because piling large quantities of soil over turfgrass is not great for the health of the turf. Some of the ants that produce larger nests include Allegheny Mound Ants (found in the Atlantic Coast of the U.S.) which can build some large and very conspicuous nests that can be over a foot tall and multiple feet wide. Additionally, since ants like to locate their nest entrances in sunny locations, they can damage vegetation in close proximity that may be shading the nest entrance. They accomplish this by biting the plants and depositing formic acid into them and, when persistent enough, can even take down larger vegetation (such as trees) through a painstaking process of hundreds of these formic acid deposits (although this isn’t very common since they prefer to nest in more open spaces).

Ants on Peonies

If you grow peonies, you may have been waiting for this section of the Ants in Our Plants blog post, as you’ve likely seen ants on or around your peonies, especially around the flowers. This is another commonly observed mutualism that exists between some flowering plants and ants (where the flowers lure ants as a source of protection from other pests), the origins of which can be traced back to the Cretaceous Period. Peonies have extrafloral nectaries located on the base of their flower buds. These produce a honeydew-like material which is a rich source of sugars, lipids, and amino acids utilized by ants as a source of food. As ants track their way to these sugary food sources, they also protect the peonies from other flower-feeding insects such as thrips. These ants don’t harm your peonies at all so there is no need to worry about them: just marvel at this cool association between two different organisms next time you are enjoying your prized peonies.

Field ants collecting honeydew-like material exuded from Peony bud.
Photo: **Whitney Cranshaw, Colorado State University, Bugwood.org**

Ants in Trees

Sometimes we can find ants in old tree cavities, and around logs and stumps. Although there are a variety of ant species that nest in these habitats, the group of ants most commonly seen in proximity to our home gardens are usually carpenter ants (Camponotus species). These ants primarily chew through dead wood, and create nesting sites in imperfections and cavities of older, often damaged and deteriorating hardwood trees. They excavate smooth nests within these cavities, and you can sometimes see a characteristic pile of sawdust around the entrance. In some situations these ants can be a structural pest in homes, especially if you have water damaged wooden structures (since damp wood is easier to chew).

They play an important role in nature by helping to break down dead and decomposing wood and cycling nutrients. In our ornamental trees, significant damage is rare and often indicates that a tree has other significant damage that is more of a concern than the ants themselves. Therefore, treatment is not usually recommended for the trees themselves, though some may choose to treat if the trees are located in close proximity to wooden structures that can potentially be damaged by these ants.

Carpenter ant nesting tunnels in dead wood.
Photo: **Joseph OBrien, USDA Forest Service, Bugwood.org**

I’m hoping that this post illuminated some of the interesting and diverse roles that ants play in and around our gardens. More than anything, though, I hope that this inspires you to be observant and to go out and explore some of these interesting and complex associations between insects and plants that we can often see in our very own backyards!

Resources

Ants in Agricultural Systems
https://www.sciencedirect.com/science/article/abs/pii/S1049964420306058
https://royalsocietypublishing.org/doi/10.1098/rspb.2022.1316

Farmer Ants and their Aphid Herds
https://www.mcgill.ca/oss/article/did-you-know/farmer-ants-and-their-aphid-herds

Mound Ants
https://www.canr.msu.edu/news/mound_ants

Ants on Peonies
https://ipm.missouri.edu/MEG/2018/5/antsOnPeonies/

Carpenter Ants
https://www.extension.iastate.edu/news/2009/jun/060503.htm

Earthworms: The Good, The Bad, and The Ugly

Earthworms have held a secure place in the hearts of many gardeners for quite some time. Charles Darwin himself was endlessly fascinated by these organisms (publishing an entire book about them in 1881) writing: “it may be doubted whether there are any other animals which have played so important a part in the history of the world…”.

Nightcrawler/Common Earthworm (*Lumbricus terrestris*). Photo: **Joseph Berger, Bugwood.org**

Recognized for their benefits to soils, including improvements in water infiltration, aeration, porosity, tilth, organic matter, beneficial microbes, and the list goes on, it is not difficult to see why. These positive impacts can be seen in home gardens and agricultural operations alike, with studies showing significant improvements in crop production correlated with the presence of earthworms. As such, terrestrial earthworms are often referred to as ‘ecosystem engineers’ due to their immense impact, and have been intentionally (and accidentally) introduced to previously worm-free areas. Many of these impacts and benefits are highlighted by Sjoerd Duiker and Richard Stehouwer’s earthworm article for Penn State Extension.

That being said, we have also started to hear a lot more about “invasive earthworms”, “jumping worms”, “stink worms”, – paired with statewide and regional campaigns encouraging people to reduce human-caused introductions and spread of non-native earthworm species in areas where they could cause significant harm to natural ecosystems and major hassles for managed ecosystems as well.

With all kinds of variable information out there, I thought it would be fitting to elaborate on the topic of earthworms, with the hopes of educating myself (and fellow readers) on some of the history, science, and misconceptions on this pretty popular garden-related topic. Having personally worked in North American horticultural systems, much of this information will be tied to the trends that we observe here, however I will also share some resources at the end that will elaborate on earthworm trends outside of North America (for those interested in learning more about the topic).

Earthworm Biology

Before we get into the nitty gritty, let’s learn a bit more about earthworm biology. There are thousands (an estimated 3000-7000) of earthworm species around the world, and these can be found on every continent except Antarctica (because earthworms cannot survive in permafrost or underneath glaciers). Most earthworm species vary in size from 10 millimeters (0.39 inches) to over a foot (12-14 inches) in length. There are even giant earthworms: such as the giant Oregon earthworm that is 4.3 feet (1.3 meters in length), the Australian giant Gippsland earthworms which can grow to 9.8 feet (~3 meters) in length, and the giant African earthworm with the largest earthworm specimen ever recorded, measuring up to a staggering 21 feet (6.7 meters) in length.

These thousands of earthworm species can be divided into 3-main groups:

Compost and litter dwellers (Epigeic)
- This group feeds on leaf/crop litter, and as such, can be found at the interface of litter and soil (around the soil surface). These earthworms are typically smaller in size than the other groups, do not consume large amounts of soil, are not as good at burrowing, and are also used in composting systems.
  Example: red wigglers (Eisenia fetida)

Topsoil dwellers (Endogeic)
- Species in this group live within the top few inches of soil, subsisting on partially decomposed organic matter present within the soil. These earthworms create horizontal burrows, filling them with their excrement (after ingesting large quantities of soil). These species can be identified by their lack of skin pigmentation, appearing grey, blue, yellow, white or pink.
  Example: angle worms (Aporrectodea caliginosa)

Subsoil dwellers (Anecic)
- This group can be found deep within the soil (up to 6 feet below the surface), living in permanent vertical burrows. They require plant residue on the soil surface in order to survive. They also ingest large quantities of soil, and deposit their excrement at the soil surface.
  Example: common nightcrawler (Lumbricus terrestris)

Three main ecological groups of earthworms. Image: Nico Eisenhauer (https://www.researchgate.net/publication/340392301_The_intestines_of_the_soil_the_taxonomic_and_functional_diversity_of_earthworms_-_a_review_for_young_ecologists)

Earthworms (Clitellata) are a class in the phylum of annelids (segmented worms). They can be characterized by their clitellum (a reproductive band that secretes a fluid to form a cocoon for their eggs). They have both male and female reproductive organs, though they require another individual for mating (where their eggs are fertilized by another’s sperm and vice versa). Depending on the species, they can produce between 3 to 1000 cocoons (containing anywhere between 1 to 10 eggs) per year. A majority of this occurs in the spring or early summer.

Like many organisms, environmental conditions and human management practices can have significant impacts on their populations and activity. Moisture, temperature, soil texture, pH, and availability of food are some of these environmental factors that can have a considerable impact. Although excess moisture is not ideal, earthworms can survive in high moisture conditions if oxygen availability in the water is sufficient. In dry conditions, they can enter a temporary hibernation stage (diapause), descend deeper into the soil, or even die (which can reduce earthworm populations in many areas during the summer months and in prolonged periods of drought).

Management practices such as reduction in tilling frequency, soil amendments (such as compost and manure), crop rotation, surface plant/crop residue, and use of certain fertilizers and lime are often linked to favorable impacts on earthworm populations. Whereas increased tillage, soil acidification, removal of surface crop/plant residue, and the use of toxic products such as certain pesticides are associated with a negative impact on earthworm populations and activity. (You can learn more about these in the Penn State Extension earthworm article).

History of Earthworms in North America

There are approximately 300 species of earthworms native to North America, and these are primarily found in previously unglaciated areas (such as the Pacific Northwest, South-Eastern U.S., Mexico, Central America, and the Caribbean). In the rest of the continent, most of our earthworm species were wiped out during the last ice age either through direct glacial cover or frozen ground (even if it was quite a distance away from the glaciers).

Image of the glacial coverage from the last ice age. Source: USGS (https://pubs.usgs.gov/gip/ice_age/ice_age.pdf)

Since European colonization of North America several hundred years ago, earthworms of European origin were introduced and have now become widespread in many areas, including those that had been previously worm-free since the end of the last ice age (such as the mid-western and northeastern U.S.). According to a 2024 study by Mathieu et al., at least 70 non-native earthworm species have colonized North America, which measures up to be 23% of the continents known earthworm species. Many of the most ‘familiar’ and commonly seen earthworm species that you may have in your landscapes may be introduced earthworms like the infamous nightcrawlers (Lumbricus terrestris), often referred to as common earthworms, which are actually European natives. These, along with around several other very competitive earthworm species have become globally widespread and some of them are even considered invasive species in many regions.

You might think, with the significant ecosystem services provided by these ecosystem engineers, is the introduction of non-native earthworm species to previously worm-free areas really that bad? The answer to this, is YES. Although the impacts of many of these non-native earthworms have been considered positive in agricultural (and home garden) situations, the impacts on natural ecosystems can result in significant ecological impacts. Additionally, not very much research has been conducted on long-term impacts of these organisms in different ecosystems. Though these effects will vary by species and ecological group, some earthworms have been associated with significant negative impacts to ecosystem processes. This has included the reduction of understory litter, impacted plant and fungal communities that are able to survive in these landscapes, has been associated with an increase in soil erosion, and had immeasurable impacts on many food webs. You can learn about the physical, chemical, and ecosystem impacts in greater detail from this publication by USDA’s Northern Forests Climate Hub.

Furthermore, some of these larger and more competitive non-native earthworm species have the potential to displace indigenous earthworm species which can often be more sensitive to soil disturbance than their introduced counterparts. The establishment of some of these non-native species around the globe can result in untold impacts on native earthworm species worldwide.

This spread followed by the immense ecosystem impacts that have and continue to occur have been dubbed by some as “global worming”.

Common Questions

Can (/should) you introduce earthworms to your garden?

Whether you have compacted soils, low organic matter, or any other reasons, you may be tempted to consider trying to boost your local earthworm populations (in order to reap all the benefits associated with them).

First of all, you should never move around invasive species, nor introduce organisms that you do not know very much about to a new landscape. Not only is it illegal in many locations to intentionally introduce certain exotic species, it can also be irresponsible. I think we all know and understand why this is a bad idea, so I won’t go into too much detail.

Even if you did become an expert in earthworm identification, and could differentiate between native vs. non-native species (and know about the established earthworms in your landscape), it still may not be a great idea to introduce earthworms to a new location (especially if you reside in one of these historically worm-free areas). We know that introductions and releases of organisms to new sites can have a variety of negative consequences (even if they may be indigenous to the area or already well-established) [many of these were mentioned in my Blog Post on Releasing Lady Beetles and Mantids for pest control in home gardens].

Even if you did manage to introduce them, they may not survive long-term nor stick around. That being said, good gardening practices may naturally attract earthworms to your gardens (without the need and potential negative impacts of introducing them yourself). So continue working on being an ecologically-responsible gardener, and enjoy the many benefits of this.

What about earthworms in my compost?

Because of earthworms’ ability to breakdown plant residues and convert them into valuable soil amendments rich in organic matter, composting using earthworms (vermicomposting) has become fairly widespread. These worm composting systems rely on earthworms such as the European red wigglers (Eisenia fetida), which are a common commercially available species. Although composting with earthworms is a well-established tool for gardeners, it is important to be a responsible vermicomposter to limit any unintended negative effects.

The contents of an indoor worm bin being assembled by gardeners at a workshop.
Photo: Abi Saeed

In areas where you do not know very much about your local earthworms and the ones that you are using in your compost (especially if you are located in previously worm-free regions), keep your worm bins contained, and do not introduce worms and cocoons in your gardens (especially if you live in proximity to natural areas). Strategies to accomplish this include creating a screen to separate your finished compost from your worms, inspecting it thoroughly for worms and cocoons and/or freezing your compost before you use it in your gardens.

Should we be working on managing these non-native earthworms?

As we know from countless examples and extensive previous experience, it is nearly impossible to eradicate established non-native (especially invasive) species. Due to the fact that many of these non-native earthworm species are widespread as a result of human transport, there is little that we can do to remove them from landscapes in which they currently thrive (especially without doing significant harm to other organisms that share those ecosystems). What we can do, however, is to limit the introduction and spread of non-native earthworm species through responsible gardening/farming (not moving around compost with earthworms or their cocoons to new sites), and recreation practices (avoiding the transport of leaves, mulch, and other plant debris into natural areas, and disposing of fishing bait appropriately).

More information on stopping the spread of invasive earthworms can be found through the Great Lakes Worm Watch campaign and land management considerations for earthworm management in areas that are worm-free as well as those with earthworm species are highlighted by the Northern Forests Climate Hub publication on non-native earthworms.

Resources:

Benefits and Biology of Earthworms (Penn State Extension)
https://extension.psu.edu/earthworms

Earthworms (Colorado Master Gardener)
https://cmg.extension.colostate.edu/Gardennotes/218.pdf

Great Lakes Worm Watch Campaign (University of Minnesota Duluth)
https://wormwatch.d.umn.edu/join-team/stop-spread

Non-Native Invasive Earthworms in the Midwest and Eastern United States (Northern Forests Climate Hub)
https://www.climatehubs.usda.gov/sites/default/files/Earthworms_CPrimer_05302024.pdf

Multiple invasion routes have led to the pervasive introduction of earthworms in North America (Mathieu et al., 2024)
https://www.nature.com/articles/s41559-023-02310-7

Earthworm Society of Britain
https://www.earthwormsoc.org.uk/

Global Distribution of Earthworm Diversity (Phillips et al., 2019)
https://www.science.org/doi/10.1126/science.aax4851

Underrated Beneficial Arthropods Part 3: Nutrient Cyclers

For the third and final installment of the Underrated Beneficial Arthropods series, I will be talking about a group of organisms that is arguably one of the least recognized and most underappreciated when it comes to beneficials. Often doing most of their work ‘behind the scenes’ the nutrient cyclers, more familiarly referred to as decomposers or saprophytes, play a crucial role in our landscapes, one that is equally as important as that of pollinators and natural enemies. Although one of the more famous examples of nutrient cyclers that many gardeners are fond of are earthworms, since these are not arthropods I will not be focusing on them in this post. (I am, however, planning on dedicating an entire post specifically to earthworms, so stay tuned for that).

According to Galente and Marcos-Garcia, 90% of the organic matter produced by green plants in terrestrial ecosystems is not consumed. The arthropods in this category provide essential ecosystem services by breaking down materials such as waste, dead plants and animals and redistributing nutrients in the soil and making them available to the plants and other primary producers (which is why they are referred to as ‘nutrient cyclers’). Although it’s not a very glamorous job nutrient cycling is essential to a well-functioning ecosystem, without which, the earth would be covered in dead plants and animals.

Like the previous posts in this series, I will be organizing this post by group of arthropods, and highlighting some of the most notable examples of nutrient cyclers in each group. This will not be an exhaustive list of all the nutrient cycling arthropods but I will include resources at the end if you want to continue to explore this topic further.

Beetles

Containing dead plant, dung and carrion (decaying animals) feeding groups, beetles (Order: Coleoptera) run the gamut of nutrient cycling roles. Some of the most well-known in this group include the charismatic black and yellow or orange carrion beetles and burying beetles (Family: Silphidae) who bury small animal carcasses into the soil, lay their eggs on them, and allow their larvae to feed on the carcasses.

American Carrion Beetle (*Necrophila americana*). Photo: Abiya Saeed

Other well-known decomposers in this group include dung beetles (Family: Scarabaeidae) which consume the feces of other animals. Due to the fact that these dung beetles process a significant amount of cattle dung and contribute greatly to the reduction of fouled forage from the accumulation of dung in livestock landscapes, Losey and Vaughan (2006) estimated the financial value of this reduction of forage fouling to be $122 million. They also play a significant role in reducing the amount of nitrogen lost to the atmosphere if dung was left on the surface to dry. By burying this dung the nitrogen is integrated into the soil making it available to plants. Sap beetles (Family: Nitidulidae) are just one example of beetles that feed on a variety of overripe, damaged, or decomposing fruit and vegetation (which may be a context that many gardeners would see them in). There are also several other beetles that shred dead vegetation such as leaflitter, bore into wood, and help create the layer of organic matter (humus) on the soil surface.

Burying Beetle (*Nicrophorus investigator*). Photo: **Joseph Berger, Bugwood.org**

Flies

Flies (Order: Diptera) also contain all the categories of nutrient cyclers- from carrion feeding to decaying vegetation and waste. Some of the most famous flies in this category are the ones that play an important role in decomposing carcasses and, as such, are important in forensic entomology. Blow flies (Family: Calliphoridae) and flesh flies (Family: Sarcophagidae) are two of the most important forensic fly families. Phorid flies (Family: Phoridae) feed on a variety of decaying plants and animals. Crane fly (Family: Tipulidae) aquatic larvae are also well-known decomposers that feed on decaying vegetation and leaf debris. Although a few species of fruit flies (Family: Drosophilidae and Tephritidae) can be important agricultural pests, other species in this group feed primarily on rotting fruit. When indoors many of these groups of flies can be a nuisance and also transmit bacteria from the surfaces on which they were feeding so controlling them in indoors is often important.

Blow Fly (Family: Calliphoridae). Photo: **Susan Ellis, Bugwood.org**

Cockroaches

Cockroaches (Order: Blattodea) often get painted with a broad brush as ‘pests or vermin’, however of the approximately 4000 species of cockroaches in the world less than 1% are considered pests of any kind. As omnivores, cockroaches can feed on a variety of materials, but many within this group are detritivores (feeding on decaying vegetation). Most of these beneficial species of cockroaches are found in leaflitter and moist areas with rich organic matter outdoors and are rarely going to enter your house, and if they do happen to get inside are only considered a minor nuisance. A well-known group of these decomposers is referred to as wood cockroaches or wood roaches.

Wood roach (*Parcoblatta* spp.). Photo: **Kansas Department of Agriculture , Bugwood.org**

Termites

Formerly in their own order (Isoptera), termites now belong to the same order as cockroaches (Blattodea) due to molecular evidence that indicates that they may have evolved from within the lineage of cockroaches. Like their cockroach relatives, these organisms often have a negative reputation since a few species of termites can be major structural pests with a significant economic impact. That being said, less than 10% of the over 2750 species of termites have been recorded as pests. The rest of this group can have significant benefits due to their feeding biology. Termites are one of the few animals that can break down cellulose (due to symbiotic associations with microorganisms in their gut) which plays an important role in helping to decompose dead woody vegetation, especially in the tropics where termites are also most abundant.

Eastern subterranean termite (*Reticulitermes flavipes*). Photo: **Phil Sloderbeck, Kansas State University, Bugwood.org**

Springtails

Springtails (Order: Collembola) are a group of impossibly adorable hexapods (six-legged organisms) but they are not considered insects. These tiny critters are found in moist environments and feed on decaying organic matter, decomposing plant materials, and fungi. They are called springtails because many in this group have a forked structure (furcula) folded under their abdomen that they can deploy to flick them upwards. If you haven’t yet seen this in action, I would strongly encourage you to check out some of the awesome YouTube videos that showcase this very cool function. These organisms are harmless to people and pets, and can easily be managed in indoor settings by reducing the moisture. Some of the most famous springtails include snow fleas which are noticeable tiny creatures aggregating on top of snow on warm sunny days.

Springtails (*Entomobrya unostrigata*). Photo: **Joseph Berger, Bugwood.org**

Isopods

Isopods (Order: Isopoda) are an order of Crustaceans that contain both aquatic and terrestrial organisms called woodlice. Of the nearly 10,000 species found worldwide about half of them are terrestrial. More affectionately referred to as pill bugs or roly-poly bugs (due to the fact that many can roll into a ball when disturbed), every child and adult has likely experienced these land isopods in an outdoor setting. They can be found in moist and dark environments such as under logs, rocks, and leaflitter. Like termites, Isopods also have symbiotic microorganisms which allow them to digest cellulose. As they break down decaying vegetation, they help improve soil quality, and make nutrients available for plant growth.

Pillbug (Order: Isopoda). Photo: **David Cappaert, Bugwood.org**

Millipedes

Millipedes (Class: Diplopoda) are a familiar and easily recognizable garden companion for a lot of us. These many-legged arthropods can be distinguished from their carnivorous cousins (Centipedes, Class: Chilopoda) by the number of legs per body segment. Where centipedes have 1 pair of legs per body segment, millipedes have 2 pairs (4 legs) per segment. Unlike their name suggests, they do not have 1000 legs, but a majority of the nearly 10,000 estimated species of millipedes fall within the range of 40 to 400 legs. Like many nutrient cyclers, they are found in damp environments where they feed on decaying vegetation and are important in making nutrients available to primary producers in the landscape.

American Giant Millipede (*Narceus americanus*). Photo: Abiya Saeed

Mites

Mites (Subclass: Acari) contain a variety of organisms that include predators and decomposers. The estimated 50,000 species of mites worldwide are fairly understudied with scientists pointing towards a potential million species that have yet to be described in this group. Oribatid mites (Order: Oribatida) in particular are key detritivores found in the top layers of soil. According to a SARE publication, they are so abundant, that a 100 gram sample of soil can contain as many as 500 individuals within 100 different genera. In fact, one of my first arthropod-related jobs was working as a lab technician on a subarctic soil mite biodiversity study where I had to sift through soil samples and photograph thousands of these nearly microscopic mites. These tiny ‘microarthropods’ are critical in breaking down leaflitter into smaller pieces which can then be further decomposed by smaller organisms. They also stimulate microbial activity by dispersing bacteria and fungi, which plays a very significant role in soil turnover.

There are many other groups of decomposers that can be found in a variety of different arthropod classes and orders but, unfortunately, the information on this topic is not as easy to find as that on pollinators and natural enemies. Although it is not a very glamorous job nutrient cyclers are critical in maintaining a healthy ecosystem by breaking down waste (such as feces, carcasses, and dead vegetation) and improving soil structure, function, and nutrient availability either directly or indirectly through their various biological functions. I hope you enjoyed learning about them as much as I did, and I especially hope that you will consider the various roles that arthropods play within their ecosystems the next time you see a familiar or unfamiliar critter in your gardens.

Resources:

Losey, J. E., & Vaughan, M. (2006). The economic value of ecological services provided by insects. Bioscience, 56(4), 311-323.
https://academic.oup.com/bioscience/article/56/4/311/229003

Decomposer insects (By: Galente and Marcos-Garcia):
https://entnemdept.ufl.edu/capinera/eny5236/pest1/content/03/2_decomposers.pdf

Burying Beetles:
https://entomology.umn.edu/burying-beetles

Dung Beetles:
https://extension.umaine.edu/blueberries/factsheets/insects/194-beneficial-insect-series-3-dung-beetles/

Sap Beetles:
https://extension.umn.edu/yard-and-garden-insects/sap-beetles

Blow Flies and Flesh Flies:
https://yardandgarden.extension.iastate.edu/encyclopedia/blow-and-flesh-flies

Wood cockroaches:
https://extension.psu.edu/wood-cockroaches

Springtails:
https://mdc.mo.gov/discover-nature/field-guide/springtails

Isopods:
https://mdc.mo.gov/discover-nature/field-guide/pillbugs-sowbugs-land-isopods

Millipedes:
https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=2345&context=extension_curall

Oribatid Mites:
https://www.sare.org/publications/farming-with-soil-life/mesofauna-arthropods/

Underrated Beneficial Arthropods Part 2: Natural Enemies

Continuing with the theme of Underrated Beneficial Arthropods that I brought up in my December post about Underrated Pollinators– I will be focusing on the next category of what I consider the trio of beneficial arthropods (which includes pollinators, natural enemies, and nutrient cyclers).

Natural Enemies

Natural enemies are comprised of predatory and parasitic arthropods, in which one or more life stages of the arthropod feed on other organisms, such as garden pests, thereby killing them. Many gardeners are familiar with this group which includes some of our most ‘famous’ predatory arthropods such as mantids, lady beetles, lacewings, etc. This category, however, contains a plethora of beneficials that you may not always think about because most of what they do often occurs behind the scenes.

This is also a very broad category so this post will not be a comprehensive collection of all the natural enemies out there (because there are literally countless) but will have a variety of some of the most abundant, important, and unique. Like the last post it will be grouped by order or major category of Arthropod, where I will go into examples of the rockstars within that category. I will also include several resources at the end which I used to compile this information and encourage those of you who want to dig deeper into the world of natural enemies to take a look.

Flies

Flies (order: Diptera) are an incredibly diverse group of insects which provide a wide variety of different ecosystem services. They undergo complete metamorphosis (which basically means that they have 4 growth stages starting as an egg, and a major transition from their larval form of maggots that turn into pupae, and then into the adults that we recognize as flies). As such, flies also inhabit countless different ecosystems (including terrestrial and aquatic) and can be found on every continent including Antarctica. We learned about pollinating flies in the Underrated Pollinators blog post but, like many of the arthropods that we are going to cover, flies span all 3 of the major categories of beneficial arthropods. We will discuss them a bit more in-depth in the nutrient cycler category, but for this post I wanted to highlight some examples of the cool predatory and parasitic flies that we can find in our yards and gardens.

Tachinid flies [Tachinidae] are dark-colored medium-sized flies that are recognized by the dark bristles covering the body of the adults (which look similar to house flies). This family contains over 8000 described species and can be found on nearly every continent. The cool thing about this group is that every single species of Tachinids has a parasitic larval stage and many are continually utilized as natural enemies of many common pest species. As such, these flies have also been intentionally imported into various locations for biocontrol purposes. The targets of tachinids include a variety of different arthropods including caterpillars, sawflies, grubs, adult beetles, and many more! To learn more about this awesome group of parasitic flies, check out this excellent article on Tachinids written by Susan Mahr of University of Wisconsin-Madison.

Adult Tachinid fly. Photo: **David Cappaert, Bugwood.org**

Hover flies [Syrphidae] also known as flower flies or ‘Syrphids’ are another awesome group (you might recognize them from their shout-out as pollinators in their bee-resembling adult stage). Larval syrphids can be terrestrial or aquatic. You may recognize the term “rat-tailed maggots” which refers to the aquatic larval syrphids that have a breathing tube resembling a ‘tail’ at the end of their body. They are used in biocontrol of a variety of soft-bodied arthropods including aphids, mealybugs, thrips, mites, and more. To learn more about hover flies, check out this excellent resource about their use as a biocontrol agent from Cornell University.

Syrphid larva feeding on oleander aphid. Photo: **David Cappaert, Bugwood.org**

True Bugs

True bugs (Hemiptera and Homoptera) contain a variety of easily recognizable garden inhabitants that can be characterized by their piercing/sucking mouthparts. Although there are many plant feeders and common pests in this category (including aphids, cicadas, mealybugs, leafhoppers, scale insects, stink bugs, etc.) there are also some excellent natural enemies that don’t always get the spotlight. Often referred to as ‘Predatory Bugs’, this fierce category of insects includes assassin bugs [Reduviidae], big-eyed bugs [Geocoridae], minute pirate bugs [Anthocoridae], damsel bugs [Nabidae], and predatory stink bugs [Pentatomidae]. They vary in shape and size, but feed in the same way: by piercing their prey with their mouthparts and sucking out the fluids. Many are, therefore, excellent biocontrol agents in our yard and garden landscapes. Some are even commercially available for use in greenhouses and hoop houses/high tunnels to suppress populations of common soft bodied insect and mite pests. To learn more about them, check out this great article on Predatory Bugs from Colorado State University.

Assassin bug feeding on elm leafminer. Photo: **Whitney Cranshaw, Colorado State University, Bugwood.org**

Wasps

Wasps (order: Hymenoptera) often strike fear in many people who are unaware of the sheer diversity and complexity of this group of insects. You learned about the pollinating wasps in my last Blog post, but there are also several groups of predatory and parasitoid wasps that are commonly found in our landscapes. Predatory wasps include many different species including the commonly known social wasp species (such as yellow jackets, hornets, and paper wasps) but also include countless other predatory species. One group of these common predators includes the striking family of thread-waisted wasps [Sphecidae]. This family includes spider-hunting wasps, cricket-hunter wasps, and katydid wasps. Another common family includes the cicada-killers [Crabronidae] which are a large and intimidating-looking wasp species that are actually harmless to humans. Both of these groups of solitary wasps work similarly by paralyzing their prey (often characterized by their common names) and then bringing their live bodies back to their underground nests for their larvae to feed on.

Cicada killer wasp carrying a paralyzed cicada back to her nest. Photo: **Ronald F. Billings, Texas A&M Forest Service , Bugwood.org**

Parasitoid wasps are an incredibly large group of wasps which include many species varying greatly in size and shape. If you’ve seen the movie ‘Alien’ you have an idea of what the life cycle of these wasps is like. The mother lays her eggs in a living host (which spans countless species of insects), and her larvae feed on the host from within, until they emerge as adults. This includes groups such as braconid wasps [Braconidae], ichneumon wasps [Ichneumonidae], and families such as Aphelinidae, Scelionidae, Eulophidae, and Trichogrammatidae. Each species of parasitoid wasp needs another species of host insect in which to complete its life cycle, and entomologists estimate that there may be hundreds of thousands of species of these incredible organisms! Many parasitoid wasp species are important biocontrol agents for some very famous insect pests (including the Emerald Ash Borer, which those of us in North America are very familiar with). You can even purchase some commercially available species of these parasitoids to manage certain pests in your gardens and greenhouses. There are even hyperparasitoids which are parasitoid wasps that specifically use other parasitic wasps as hosts. To learn more about the incredible world of wasps, check out this great article by Marissa Schuh from University of Minnesota.

A tomato hornworm caterpillar parasitized by braconid wasps that have emerged from internally feeding on the caterpillar, and exited their white silken pupae as adults. Photo: **Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org**

Beetles

Beetles (order: Coleoptera) are one of the most diverse groups of insects and include groups that fall into each of the three categories of beneficial arthropods. Although some are pests in their larval and/or adult stages (example: Japanese beetles) and feed on a variety of different plant structures including leaves, stems/trunks, fruit, flowers, seeds, and roots. We are also familiar with some of these predatory beetles (with many shining a spotlight on the easily recognizable and lovable lady beetles). That being said, there are countless other groups of predatory and parasitic beetles that can have a significant beneficial impact on our landscapes.

A violet ground beetle (*Carabus violaceus*) which is a nocturnal hunter of slugs. Photo: **Mary C Legg, Mary C Legg, Bugwood.org**

One example of a large group of these are the predatory ground beetles [Carabidae]. This dark and iridescent family of beetles can vary in size and shape. They have distinct and powerful chewing mouthparts (mandibles) which enable them to be excellent generalist predators and scavengers. The more than 40,000 species (spanning every continent except Antarctica) are common garden-inhabitants and perform invaluable services of biocontrol in agricultural, horticultural, and home garden settings.

In addition to feeding on many insect and mollusc pests, certain host-specific groups of plant-feeding beetles are also used in the biological control of weed species (including many noxious weeds) and reared by insectaries for distribution.

Neuroptera

Neuroptera (derived from the Greek words meaning “nerve” and “wing”) is an entire order consisting only of predatory insects! The most famous of this group are the lacewings [Chrysopidae] (which many gardeners recognize as an awesome predator of many soft-bodied garden pests). This order also includes other incredible species such as antlions or “doodle-bugs” [Myrmeleontidae], dobsonflies [Corydalidae], mantidflies or mantid lacewings [Mantispidae], snakeflies [Raphidiidae], and more.

Lacewing larva feeding on potato psyllid. Photo: **Whitney Cranshaw, Colorado State University, Bugwood.org**

Mites

Mites (subclass: Acari) are another often misunderstood group of arthropods. These are arachnids (characterized by 4 pairs of legs and two body segments). Mites feed on countless living and decaying organisms including plants, animals, fungi, yeasts, algae, mosses, and even bacteria. They range in size, though most are tiny and many are even microscopic soil-dwelling organisms. The sheer diversity of mite species (due to their very broad range of ecological roles) indicates that there may be over a million species that have yet to be described.

Many gardeners recognize some common mite pests (such as the two-spotted spider mite), but there are countless predatory mite species as well. Predatory mites [Phytoseiidae] are slightly larger than spider mites, and excellent predators of spider mites and eriophyid mites which are common plant-gall causing mites. There are several species used in biocontrol of soft-bodied insect and mite pests as well as commercially available ones that you can purchase.

Spiders

I am sure that no one reading this post would be surprised to find these amazing arachnids on this list. Although some species are dangerous to humans, most species of spiders will leave you alone, and are incredible predators of lots of indoor and outdoor insect pests. Many humans dislike these 8-legged organisms, though most are still understanding of the important role that they play. Spiders can be strikingly beautiful, colorful, and variable in size and shape. Although some build webs to capture prey, others are active hunters or trappers that capture other organisms on which to feed. Some are even kept as pests (I had 4 tarantulas of my own at one point, and I thoroughly enjoyed observing them daily, and handling the more mild-mannered ones). There is so much that can be said about the incredible role of spiders in our homes, gardens, and natural ecosystems that it would be difficult to condense into a short summary (and may therefore be a separate Blog post in the future since this one is getting pretty lengthy).

Jumping spider. Photo: **Joseph Berger, Bugwood.org**

Centipedes

Centipedes span 4 different orders including soil centipedes [Geophiulomorpha], garden/rock centipedes [Lithobiomorpha], giant centipedes [Scolopendromorpha], and house centipedes [Scutigeromorpha] all of which are carnivorous. This group of arthropods is characterized by many body segments, venomous fangs, and 1 pair of legs per segment. Although many people are creeped out by these ferocious many-legged beasts, they stay out of the way and eat many common pests in home and garden landscapes.

Stone centipede. Photo: **Joseph Berger, Bugwood.org**

I hope that you enjoyed reading about some of your gardening companions, and if nothing else: I hope that it broadened your perspective of all the different critters that share your landscape with you. Stay tuned for my next post in June, which will cover the third and final category of beneficial arthropods: the nutrient cyclers.

Resources

Natural Enemies of Pests. (Colorado State University).
https://agsci.colostate.edu/agbio/ipm/natural-enemies-of-pests/

Tachinid Flies. (University of Wisconsin-Madison).
https://hort.extension.wisc.edu/articles/tachinid-flies/

Syrphid Flies. (University of Minnesota Extension).
https://extension.umn.edu/beneficial-insects/syrphid-flies

Hover Flies. (Cornell University).
https://cals.cornell.edu/new-york-state-integrated-pest-management/outreach-education/fact-sheets/hover-fly-biocontrol-fact-sheet

Wasps are a gardener’s friend. (University of Minnesota Extension). https://extension.umn.edu/yard-and-garden-news/wasps-are-gardeners-friend

Cicada Killer Wasps. (University of Kentucky).
https://entomology.ca.uky.edu/ef004

Parasitoid Wasps. (University of Minnesota).
https://extension.umn.edu/beneficial-insects/parasitoid-wasps

Hyperparasitoid Wasps. (North Carolina State University).
https://entomology.ces.ncsu.edu/biological-control-information-center/beneficial-parasitoids/hyperparasitoids/

Predatory Ground Beetles. (Colorado State University).
https://agsci.colostate.edu/agbio/ipm-pests/ground-beetles/

Biological Control of Weeds. (Washington State University).
http://invasives.wsu.edu/biological/index.htm

Underrated Beneficial Arthropods Part 1: Pollinators

The world of beneficial arthropods (insects and their relatives) far exceeds some of the common critters that we often associate with this category. Many of them perform vital functions in our own yards, gardens, and ecosystems all over the world. A very small sliver of all arthropods are considered pests of any kind though there are certainly some pretty devastating pests in this category. Most of these other organisms are either providing benefits or maintaining important ecosystem functions. They are often overlooked, as some of the more charismatic ones (like butterflies, bees, mantids, and lady beetles) take most of the spotlight. These other not-so-glamorous beneficial arthropods are just as important as the more famous ones, and often perform many tasks that go unseen and underappreciated.

I wanted to talk about each group of common beneficial arthropods (Pollinators, Natural Enemies, and Nutrient Cyclers), but as I was writing, I admittedly got a bit carried away. So in order to prevent this blog post from being extremely long, I decided to split this into 3 parts. Stay tuned for the next installments in my spring and summer GP blog posts. In the meantime let’s dig into some under-appreciated pollinators.

Underrated Pollinators

Goldenrod Soldier Beetle ( *Chauliognathus pensylvanicus*) feeding on pollen. Photo: Abiya Saeed

Ah yes, pollinators! Many people consider this their favorite category of beneficials (because very few things are as striking or charismatic as a bee or butterfly sipping nectar from a flower). This is also one of the first groups that come to mind when people think about beneficials in general. The classic image of a monarch butterfly or a honey bee on a flower is often associated as the representative image of this group. That being said, honey bees are just one example of the over 20,000 bee species that are found worldwide. But this group far exceeds butterflies and bees- and some of the less charismatic critters often get an unfair reputation, or just a lack of awareness about what they do. For a variety of reasons, including their anatomy, efficiency, abundance, and direct economic impact, bees are considered the most important pollinators. But many other animals are also great pollinators, some of which are the sole pollinators of certain plant species. In fact most arthropods that visit flowers have the potential to move pollen around, making them possible pollinators. But since I don’t have time to write a whole book’s worth of information into this blog post, I will focus on a few of the larger groups of these less famous pollinators. If you are interested in doing a deeper dive into the world of beneficial arthropods, I will include some resources at the end.

Flies

Flies (order: Diptera) are a huge group of insects, with over 110,000 described species in 150 different families. This group spans a wide variety of very well-known groups like house flies [Muscoidea] and mosquitoes [Culicidae], to not so well-known groups like stalk-eyed flies [Diopsidae] and long-legged flies [Dolichopodidae]. They encompass nearly all biomes and have a broad range of functional groups including predators, parasites, decomposers, and pollinators. In fact, some studies consider flies to be the second most important flower visitors after bees.

Green Bottle Fly (*Lucilia* sp.) on a Prickly Pear (*Opuntia* sp.) Photo: Abiya Saeed

According to a literature review by Cook et al. (2020): flies from 86 different families have been reported to visit over 1100 plant species. These flower-visiting fly species also include some that have important potential for crop pollination and have been recorded to visit many horticultural crops. This includes commonly known pollinating flies, e.g., bee flies [Bombyliidae], hoverflies [Syrphidae], and flower flies [Anthomyiidae]. But some flies we don’t usually associate with this role such as blow flies [Calliphoridae], flesh flies [Sarcophagidae], and horse flies [Tabanidae], and some that many may never have heard of such as nose flies [Rhiniidae] and march flies [Bibionidae], are included. Some species are even considered to have potential as managed pollinators, a role that we most commonly associate with honey bees and some other bee species.

Fun fact: only female mosquitoes need a blood meal in order to reproduce, whereas male mosquitoes feed on nectar, making mosquitoes pollinators! In fact, mosquitoes have been studied as pollinators of orchids, like the Blunt-leaf Orchid, Platanthera obtusata, among other plants.

Moths

We all know butterflies and moths (order: Lepidoptera) are well-documented flower visitors and important pollinators. Despite this, butterflies often get most of the limelight and attention from the general public while many moths often end up being overlooked. Even though moths make up nearly 90% of the over 160,000 described Lepidoptera species, there is a disproportionate amount of research that has historically been conducted on them when compared with butterflies. It has also been demonstrated that moths are the most important nocturnal pollinators, which is fairly intuitive when you think about their nocturnal foraging biology. A study conducted in Sussex by Anderson et al. (2023) demonstrated that moths had higher pollen deposition rates on bramble species indicating that they are more efficient pollinators of brambles than their diurnal counterparts. This has implications for the importance of moths in other plant groups as well, as new research continues to be conducted.

Clearwing Moth (*Hemaris* sp.) Photo: **Steven Katovich, Bugwood.org**

Fun fact: My favorite story to tell about plant-pollinator interactions is of Darwin’s Star Orchid (Angraecum sesquipedale). Charles Darwin was sent a sample of this striking orchid from Madagascar in 1862. Upon examination he found that the nectar tubes were 30 cm (~12 inches) deep! Based on this, Darwin hypothesized that it would take something that has a really long tongue to be able to access that nectar but nobody believed there could be such an insect and he was ridiculed by other scientists. In 1867 Alfred Russel Wallace examined the orchid and predicted there must be a moth in Madagascar that can reach this nectar in order to pollinate the plant. But no moth had ever been discovered which had a proboscis (a coiled and elongated mouthpart of butterflies and moths that is used to suck up nectar) that long. It wasn’t until decades later in 1903 a moth meeting these specifications was discovered. Aptly named in honor of the scientist who predicted its existence, Wallace’s sphinx moth (Xanthopan praedicta) also known as the ‘predicted moth’ has the longest proboscis (sometimes referred to as a tongue, though it is not quite a tongue) of any insect. This just demonstrates just how amazing plant and insect interactions and coevolutionary relationships truly are!

The Star Orchid alongside the ‘Predicted Moth’! Photographed by Robert Clark for Evolution

Wasps

Wasps are in the order Hymenoptera, shared with bees and ants. They often have a bad reputation due to a few particularly aggressive social wasp species that most of us have likely had an unfortunate interaction with. That being said, the wasp group is extremely large, diverse, and species-rich. With over 103,000 described species in the category (and scientist estimates stating that the actual number could be in the millions), wasps span a lot of crucial categories of beneficials including parasitoids, predators, and pollinators.

Many wasp species resemble bees and it can be easy to confuse them for each other when they are visiting flowers. The major differences between the two are the thread-like waist that wasps have, and their less-hairy sometimes shiny, overall appearance. In addition most wasp species are primarily carnivorous, feeding on insects and other sources of meat for their protein needs, making them a great resource for deterring common garden pests (stay tuned for more on that in the next part of the Underrated Beneficials series). Even though most of these wasps are carnivorous, they supplement their diet with sugars which they often get from nectar or honeydew produced by sap-sucking insects, e.g., aphids, and occasionally fruit.

White-Striped Black Mason Wasps ( *Pseudodynerus quadisectus* ) mating on a Goldenrod (*Solidago* sp.) Photo: Abiya Saeed

There are also some species of vegetarian wasps. A common example of these are the 300 species of pollen wasps (Masarinae) which, like bees, are nectar and pollen feeders (and many of which are important pollinators of certain plant species, such as the Water Leaf, Hydrophyllaceae). Due to the fact that they have fewer hairs, wasps aren’t as efficient at pollination as bees, however, they can still be very important pollinators. Like bees, some wasps are generalist pollinators, visiting a wide-array of flowering plants, while others are specialists where a group of wasps relies on a group of flowering plants and vice versa. In these cases the pollination of those plants are reliant on these wasps.

Studies have shown that some generalist wasp species are better than some generalist bees at pollinating specific flowers. A 2018 study by Thomson examining the pollinators of the California Bee Plant (Scrophularia californica) showed that the western yellowjacket (Vespula pensylvanica) was a more effective pollinator in terms of pollen deposition when compared with honey bees and bumble bees. Some species of African pineapple lilies (Eucomis autumnalis and Eucomis comosa) and African milkweed (Pachycarpus grandifloras) are primarily pollinated by spider-hunting wasps (Pompilidae) in the genus Hemipepsis. Additionally over 100 species of orchids are reliant on wasps for pollination some of which use sexual mimicry to attract male wasps to flowers! And I would be remiss if I didn’t mention fig wasps (family: Agaonidae), who have been coevolving with their host plant for tens of millions of years. The fig (Ficus sp.) ‘fruit’ is actually an inflorescence (an enlarged stem with lots of little flowers inside). In order to pollinate those flowers, the female fig wasp squeezes into a small opening and moves around, laying her eggs in the ovaries of these flowers thereby spreading pollen from the fig that she was born in. The male offspring will remain in the fig while the new batch of females will emerge and look for a new fig in which to lay their eggs (see resources for more on this fascinating mutualism).

For more information on wasps as pollinators, check out the awesome article by Hooks and Espíndola, linked in the resources!

Fun fact: Sexual mimicry is used by some flowers to attract their pollinators. In these situations, the flowers use a combination of visual and chemical cues including mimicking the scent of specific female wasps and bees to attract males. An example of this can be seen in the wasp family Thynnidae, where male winged-wasps are searching for wingless females to mate with. When they stumble across the warty hammer orchid (Drakaea livida) they confuse it with a female thynnid wasp, because of the similar shape and scent, and try to mate with it. This process results in the pollen being deposited on the abdomen of the male wasp. As he goes to the next orchid in order to mate, the pollen is deposited on the new flower, resulting in pollination.

Beetles

Beetles (order: Coleoptera) are considered to be the largest insect order with over 350,000 described species, which makes up 25% of all known animal species on Earth! Like some of the previously mentioned orders, they include a large diversity of functional groups, including pollinators. Due to the incredible size of this order, they are considered to be the largest and most diverse group of pollinators with an estimated 77,000 flower-visiting species. In fact, based on pollen-covered specimens preserved in amber from 100 million years ago which is 30 million years earlier than the first records of bee pollinators, beetles are considered to be the first recorded insect pollinators! Even now they are considered to be vital pollinators of some of the most primitive flowering plant groups that still exist today, such as Magnolias.

Flower Longhorn Beetle (*Analeptura lineola*) on a Multiflora Rose (*Rosa multiflora*). Photo: **Ansel Oommen, Bugwood.org**

Although some beetles are specialists of certain plant groups ,especially those that are descendants of some of the earliest flowering plant groups including water lilies and magnolias, most are generalist pollinators and will visit a wide array of flowering plants. Some scientists even estimate that flower-visiting beetle species will visit 90% of all 350,000 flowering plant species. Beetle pollination is also essential for certain agricultural crops including Paw Paw (Asimina sp.) and the Atemoya (Annona x Atemoya).

For more information on the fascinating world of beetle pollination, check out the awesome article by Hooks and Espíndola, linked in the resources!

Fun fact: The process of cross-pollination that depends on beetles is referred to as ‘cantharophily’.

Resources

Cook et al. (2020). The Role of Flies as Pollinators of Horticultural Crops: An Australian Case Study with Worldwide Relevance. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7349676/

Anderson et al. (2023). Marvellous moths! Pollen deposition rate of bramble (Rubus futicosus L. agg.) is greater at night than day. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0281810

Hooks and Espíndola. (2017). Wasps, surprisingly cool pollinators. https://blog.umd.edu/agronomynews/2020/08/31/wasps-surprisingly-cool-pollinators/

The story of the fig and its wasp. https://www.esa.org/esablog/2011/05/20/the-story-of-the-fig-and-its-wasp/

Hooks and Espíndola. (2017). Beetles and Pollination.
https://blog.umd.edu/agronomynews/2020/06/29/beetles-and-pollination/

The Fascinating Phenomenon of Fasciation

You may have seen it on the odd flower or plant here and there or you may be intentionally growing plants that show this unique and uncommon phenomenon. Fasciation (not fascination- though it certainly is pretty fascinating) is a malformation or abnormal pattern of growth in the apical meristem (growing tip) of plants. The apical meristem is undifferentiated tissue that triggers the growth of new cells (which extends roots and shoots, and gives rise to stems, leaves, and reproductive structures). In the case of fasciation (which originates from the Latin ‘fascia’ which means ‘band’ or ‘bundle’), this new growth is abnormal and often appears as flattening, ribboning, swelling, fusion, or elongation of plant parts. Sometimes referred to as ‘cresting’, this can occur anywhere on the plant but is more likely to be seen in stems, flowers, and fruit. You might encounter this as several stems growing together, a multi-headed or misshapen flower, perpendicular or irregular growth, dense tuft-like growth, or coiled, contorted, and twisted stems which can sometimes have an unusually high concentration of leaves and flower buds.

A fasciated hinoki false cypress ( *Chamaecyparis* *obtusa* ) (Photo: **Anton Baudoin, Virginia Polytechnic Institute and State University, Bugwood.org** )

There are multiple patterns of fasciation that can be observed, including: linear fasciation (which results in the more common flattened and ribbon-shaped stems), bifurcated fasciation (when a linear fasciation splits in two to form a “Y” shape), multiradiate fasciation (where the stems split into three or more short branches, referred to as a ‘witches’ broom’), or the rare ring fasciation (where the growing point folds over to form a hollow shoot) (Geneve, 1990).

A ribbon of fasciated stems (Photo: **Joy Viola, Northeastern University, Bugwood.org** )

Fasciation is a symptom that can be caused by a variety of different factors including genetics, hormones, pathogens (including bacteria, viruses, and phytoplasmas), injury (including chemical, mechanical, and feeding damage), nutrient deficiency, or environmental causes (such as temperature extremes) though in many cases it is still not completely understood and the exact cause may not be apparent in a specific fasciated plant. The stability of this phenomenon is also pretty variable. Some plants can pass on this trait through their seeds (resulting in a genetic likelihood of expressing this symptom), while other plants can develop fasciation (through a variety of causes) and then resume normal growth from a fasciated point, or perennial plants that appear fasciated one year may be completely normal the next year. Scientists have even identified some of the specific genes in which mutation can cause fasciation and have experimentally reproduced this result in seedlings that were exposed to radiation, chemical mutagens, and high temperatures.

Fasciated Gaillardia showing unusual growth in the stems and flowers (Photo: **Department of Plant Pathology , North Carolina State University, Bugwood.org** )

Most often fasciation is just an aesthetic anomaly, is fairly uncommon, and rarely impacts the survival of affected plants (especially if they are established woody plants). In cases of fasciation due to infection by certain pathogens (such as the bacterium Rhodococcus fascians), it is possible for affected plant parts to die prematurely. Although infectious fasciation can spread to other susceptible plants, in the majority of cases fasciation is not infectious and will not spread.

Fasciated asparagus (Photo: **Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org** )

Although fasciation can occur on any plant (and has been documented in hundreds of plant species) it is more frequently seen in certain groups such as cacti, daisies, asters, legumes, willows, and plants in the rose family (Rosaceae). It is also more common in plants with indeterminate growth.

Crested saguaro cactus (*Carnegiea gigantea*) (Photo: **Joy Viola, Northeastern University, Bugwood.org** )

In some cases, distinct examples of fasciated plants are intentionally selected for their visual appeal and interest. Many times, plants that have a greater propensity for fasciation, or those that can be vegetatively propagated are developed into cultivars that can be sold (and are often a striking addition in any garden). Many of our dwarf conifers, for example, are propagated from witches’ broom cuttings. In addition, some of our large and uniquely shaped tomato varieties, such as beefsteaks, are selected for their fasciated fruit, and many strawberries that have a wider shape or appear to be ‘fused together’ are also fasciated and considered desirable.

Beefsteak tomatoes are a common example of desirable fasciated fruit. (Photo: Lufa Farms, Wikimedia Commons)

Examples of plants that frequently exhibit fasciation, including those with cultivars that you can purchase for your gardens, are ‘cockscomb’ celosia (Celosia argentea var. cristata), ‘fascination’ culver’s root (Veronicastrum virginicum or sibiricum ‘Fascination’), ‘crested’ hens and chicks (Sempervivum spp. var. cristata), and Japanese fantail willow (Salix sachalinensis ‘Sekka’), among others.

Fasciated cockscomb (*Celosia argentea* var. cristata) (Photo: **Julia Scher, Cut Flower Exports of Africa, USDA APHIS PPQ, Bugwood.org** )

If this strange growth is something you don’t enjoy, you can prune out the distorted tissue. Or if you’re like me – you can just marvel at the weird and the wonderful!

Fasciated Yucca flower stalk (Photo: **USDA Forest Service – Rocky Mountain Research Station – Forest Pathology , USDA Forest Service, Bugwood.org** )

Resources

Fascinating Fasciation (Wisconsin Master Gardeners):
https://mastergardener.extension.wisc.edu/files/2015/12/fasciation.pdf

Plant of the Week: Fasciated Plants (University of Arkansas):
https://www.uaex.uada.edu/yard-garden/resource-library/plant-week/fasciated-2-22-08.aspx

The Genetics of Fasciation:
https://trinityssr.files.wordpress.com/2016/06/4th-ape.pdf

Fasciation (University of California IPM)
https://ipm.ucanr.edu/PMG/GARDEN/FLOWERS/DISEASE/fasciation.html

Fascinated with Fasciation (Dr. R. Geneve, 1990, American Horticulturist)
https://ahsgardening.org/wp-content/pdfs/1990-08r.pdf