Insects and Fertilization

Linda got a few comments and questions on her post a couple of weeks ago on fertilization and insect resistance.  This is an issue I’ve been peripherally involved with over the years so I wanted to share a few thoughts.  First, the relationship between plant nutrition and insect resistance is extremely complex.  We often have difficulty predicting how a plant is going to respond to fertilization, let alone predict how an insect is going to respond to how the plant responded.  I haven’t kept up but Koricheva (2002) reported over a dozen different theories have been proposed to explain insect response to plant nutrition.  One of the factors that makes it difficult to generalize about plant/insect interactions is that various insects feed on different plant parts in different ways; some are leaf feeders, some suck sap, some bore into wood, some feed on seeds or cones.  How an insect feeds can affect its response.  To stick with an illustration I’m more familiar with, we can look at insect response to plant drought stress.  Bark beetles are widely known to key in and attack pines and other conifers under drought stress but pine tip moths prefer succulent buds and new growth and are more likely to attack well watered trees.  It’s not unreasonable to think there are similar differences with nutrition.

 

Nevertheless, as noted above, there have been attempts to come up with general theories on the effect of plant nutrition on insect resistance.  One of the most widely cited is the Growth-differential balance theory proposed by Dan Herms and Bill Mattson  (“The dilemma of plants: to grow or defend.”  Q. Rev. Biol. 67: 283-335).  A quick check on Google Scholar indicated this paper has been cited by over 1,400 other papers, which is an astounding number and speaks to its influence.  The basic premise of the theory, as suggested by the title of the paper, is that plants make a trade-off between allocating carbohydrates for growth or allocating carbohydrates for secondary defense compounds.  Dan Herms subsequently applied the theory in synthesizing the literature on woody ornamentals in his 2002 paper,  “Effects of Fertilization on Insect Resistance of Woody Ornamental Plants: Reassessing an Entrenched Paradigm.” (Environmental Entomology 31(6):923-933.).  I have heard some arborists and others use this paper to argue that we shouldn’t fertilize landscape trees at all.  The problem is they oversimplifying the theory – which is understandable, this is pretty heady stuff.  They get the ‘trade-off’ idea; if plants grow fast they produce lots of yummy stuff for bugs.  But what is often overlooked – even though Herms makes a point to say it – is that when nutrition or other plant resources are low; there is no trade-off.


This figure from Herms and Mattson illustrates the idea.  If nutrients are deficient and we fertilize a plant the plant may increase growth and secondary compounds; it’s not always an either/or situation.  The bottom-line remains the same;  nutrient deficient plants can benefit from fertilization or correcting the factors (e.g., alkaline pH) that made them deficient in the first place.

Koricheva, J. 2002. The Carbon-Nutrient Balance Hypothesis Is Dead; Long Live the Carbon-Nutrient Balance Hypothesis? Oikos 98 (3): 537-539

Proposed phosphate fertilizer ban

Today I received an email alerting members of Washington Friends of Farms and Forests to a proposed ban on phosphate-containing fertilizers in the state of Washington.  Here’s part of the text of the email (I’ve removed underlining, bolding, highlighting etc. so this reads as objectively as possible):

“Concerns with the HB 1271 & SB 5194 banning the sale of fertilizer containing phosphorous:

1) The intent section contains scientifically inaccurate statements, creating a false precedent that turf fertilizer is a significant surface water pollutant and is not necessary for a healthy lawn.

2) It grants the authority to regulate fertilizer sales and use to the Department of Ecology (Currently, the Department of Agriculture regulates fertilizer content and registers it for sale.)

3) It changes the definition of fertilizer used by the Department of Agriculture, creating confusion.

4) It is inconsistent and will be ineffective because it exempts “natural organic sources.” Organic products are high in phosphorous. The ecosystem cannot tell the difference. All fertilizer should be regulated equally.

5) It fails to recognize the expertise of trained lawn care professionals, who should not be prohibited from providing quality service to their customers, including publicly owned golf courses, parks, and sports fields.

6) As written, it bans the use of phosphorous fertilizer for forestry, house plants, shrub beds, golf courses, sports fields and other uses. It is unclear as to private commercial property.

7) It bans the sale of phosphorous fertilizer for flower and vegetable gardens, forestry, house plants, shrub beds, golf courses, sports fields, and many other uses.

8) It bans retailers, including farm stores and ag dealers, from displaying any type of fertilizer containing phosphorous.

9) It fails to address the primary causes of impaired water quality. Regulating something because it’s easy without addressing root causes of the problem accomplishes nothing.”

So, readers and colleagues, do a little homework over the weekend.  Look at the bill itself (both the house and senate bills are the same; the link is for the house bill).  Are these nine concerns valid?  Discuss.

When trees attack!

I’ve been suffering through my post-holiday, post-annual-reporting cold and/or flu, so I don’t feel as witty (or snarky) as I might otherwise be.  Instead, I feel like my body’s been invaded by a slowly spreading mass that reminds me…oh, I don’t know…of what trees can do when they encounter an immovable object.

Not much of a segue, I know, but I just had the urge to post some interesting photos after Holly’s photo-fest yesterday.  (Memo to self: not fun being Holly’s follow-up act.)  Anyway, you’ve seen what happens when growing trees encounter neglected plant tags:

And perhaps you’ve seen how roots laugh at puny planting pits:

So before you feel the urge to attach something – anything – “permanently” to a tree, keep in mind that they have no respect for authority…

…or even those who got them started in life:

Winter Trade Show Report

Disclaimer: The information and images below should not be construed as any sort of recommendation, remedy or advice. Just some cool and/or weird stuff I saw at a green industry trade show. Plus this blog needs more photos.

Was at the Mid-Atlantic Nursery Trade Show (MANTS… and yes, there is a Pennsylvania version…PANTS) in Baltimore a couple of weeks ago.  It’s a wonderful opportunity to visit with past students (now gainfully employed – yay!).  I also get to personally thank the nurseries and other businesses that generously support our Horticulture Department and Garden.  I’m more "herbaceous" so I tend to get more (professionally…and emotionally) out of the floriculture summer trade show and conference in Columbus, Ohio (OFA)  If you dig hot new tropicals, annuals, and perennials – it’s THE place to be.  MANTS tends to be more landscapy/woody.  There are umpteen wholesaler booths filled with dormant, ball & burlapped trees and containerized shrubs. There are WAY too many Bradford pears still out there (see Bert’s post below).  Honestly. 

Foot traffic was good (10,000 + registrants) for the 300 exhibitors: wholesale nurseries, garden center suppliers, liner and plug growers, landscape and nursery equipment manufacturers.  Also, all of the allied businesses you might not think of – inventory software, nursery insurance companies, universities and colleges, grower organizations, tag and pot manufacturers, etc.,  always a fascinating vertical and horizontal cross section of this business of growing and selling plants.

On with the show…

Propagation nurseries make the world go ’round.
This IS the proverbial candy shop for greenhouse and nursery growers.  Each flat holds 36, 78, or 105 little plants.  Two flats…would fit in my tote bag. Heh.


Succulents continue to be hot. Here’s Kalanchoe thyrsifolia ‘Fantastic’.
Fantastically awesome.


Even better…check out the pot made from (very) compressed rice hulls. Nice color, pretty shape, biodegradable. You’ll probably see more of these in the near future.


Display promoting the book "Creating a Deer and Rabbit-Proof Garden".  Artificial flowers – that may be the ticket…no, wait, it’s an artificial deer, too.


WANT. My 1972 John Deere 750 is on its last legs/tires. Plus this one would fit down our blueberry rows, AND it has a cup holder.  The brochure is now pinned above my desk.

Great name for a nursery:

that’s Holly, Woods, and Vines if you can’t read it.

Also the home of…


Faux moss-covered faux rocks. Intriguing.

Finally, there’s always a peek at trends in pots (pottery pots), garden art (tasteful or not) and other items coming soon to your local independent garden center…


Lots of antique and rustic looks out there, also galvanized is big.
I loved the fishy pots. Alas, one can only look, and then place an order. Minimum quantity – one pallet. Maybe if we all went in together…

Warning: This blog may be hazardous to your health

Following up on Jeff’s post last week regarding blue spruce.  Jeff noted, and several posters agreed, that even though blue spruce will eventually have a host of pest problems, for the first 10 years or so it’s a darn good looking landscape conifer.  Jeff went on to draw the analogy that choosing a blue spruce is like choosing sexy sports car or gas guzzler over a boring, high MPG sedan.  To a certain extent the libertarian in me agrees.  If I want to plant a blue spruce in my Michigan backyard or buy a Nissan Titan to commute back and forth to work , by Gawd, that’s nobody’s business but my own.  Of course the difference in these situations is that I have EPA reporting to tell me the Titan only gets 12 MPG in the city; for the spruce, people like Jeff, me, and our highly intelligent readers know what we’re getting into from experience and training.  But what about the public at large?  Maybe what we need are government warning labels for plants.  We have them for cigarettes: “Warning: Smoking Causes Lung Cancer, Heart Disease, Emphysema, And May Complicate Pregnancy”, though the European warning, “Smoking kills” is more direct and to the point.  We also have warnings for side effects of prescription medications; “may cause nausea, vomiting, headache, hearing loss, oily discharge, an erection lasing four hours, and thoughts of suicide”.  Think I’ll take my chances with the disease, thank you.  

 

So what kind of labels do plants need?

 

Blue spruce:  Warning this plant will look great in your yard for 10 years and then fall apart when it becomes a magnet for gall adelgid and loses half its limbs to cyctospora.

 

Eastern white pine:   Caution: This little guy looks like a cute little Christmas right now but in 10 years it can devour your house.

 

Silver maple:  Warning:  Don’t blame us when this tree comes crashing though your house during windstorm.

 

Sweetgum:  Caution: Be sure to retain a good attorney for when your neighbors start tripping over gumballs on the sidewalk.

 

That’s a start. What plants do you think need warning labels?

Porsche 911 or Toyota Camry

Earlier today I was in a meeting with some other professionals from across Minnesota (and a few from Wisconsin and other areas) to discuss the disease problems of conifers.  Our discussion quickly became focused on the use, and overuse, of Colorado blue spruce, a tree that just doesn’t do well in Minnesota — Or Michigan from what Bert has written!  Everyone in the meeting was yammering on about how we need to educate nurseries and consumers about how terrible the Colorado blue spruce is in our environment — you’re lucky if you can get 10-15 years out of the thing before it succumbs to one disease or another.  But, though academics, arborists, and most tree care professionals (including nurserymen) talk about how lousy this tree is, customers want Colorado blue — and if a nursery doesn’t sell it, well then that nursery has lost some business.

I support the idea of warning people away from Colorado blue.  Still, during our meeting I couldn’t help but have this thought running through my mind:

Colorado blue spruce is a unique and beautiful tree — it is bluish in color, tends to have a good form, and is a relatively fast grower (until it succumbs to whatever disease it dies from!).  There are certainly other trees that are also beautiful — but there is no denying that Colorado blue has a distinctive look.  If I were walking through a nursery this would be the tree that I’d want.  If a nursery person told me that the tree was going to have a short life — 10 – 15 years of looking good — I just might be OK with that because there just aren’t that many trees which look as attractive as a Blue spruce in a nursery.  Sure, I could have something that would look OK for 30 years, but, if I’m like most Americans, I won’t even be in the house that I’m living in now in 10 years, never mind 30.

To draw an analogy, You know that a Porsche 911 isn’t the best car to buy — it is a gas guzzler (for it’s size) — it doesn’t have much luggage space (or room for passengers), and it’s less reliable than your typical compact car.  A Toyota Camry is better in all of the areas that I just mentioned.  Still, if I were looking for a car and if they were the same price I have to admit that the Porsche would be too cool to pass up.

Fast food is unhealthy for plants, too

In early December, I posted my thoughts about fertilizing crops vs. landscapes.  An anonymous reader asked if we could follow up by discussing the relationship between excessive fertilizers and plant susceptibility to pests and disease.  It’s taken a month to get the scientific literature (and my act) together, but here it is.

There are decades’ worth of articles about the direct relationship between increased nutrient availability and increased susceptibility to pests, disease, and disorders.  One of the earliest articles linked the incidence of celery blackheart to over-fertilization.  Since that time, researchers have found similar causal relationships in vegetable crops such as rice, onions, and soybeans, ornamental crops including poppies, and perennial orchard crops such as nectarines.  Unfortunately, there’s been no research on landscape species.

Happily, the way plants react to excess nutrient levels is generic – so we can apply the findings in the agricultural literature to landscape situations.  Just like kids and candy, plants will greedily take up all the available macronutrients their roots can find, especially nitrogen and phosphorus.  (It makes NO difference is the fertilizer is organic or inorganic.)  Plants in highly nutritive soils respond with lush vegetative growth – and fewer flowers, by way.  Less metabolic energy is put into protective compounds, so these succulent new leaves and shoots are prime targets for all kinds of unwanted plant-eaters and foliar pathogens.

As with so many things in life, moderation is the key.  For routine landscape needs, use woody mulches rather than fertilizers and nitrogen-rich composts.  This “slow food” approach not only benefits your plants, but provides ideal habitat for mycorrhizal species, which have been shown to help restrict root uptake of excessive nutrients, while assisting with uptake of less available ones.

A comment about home remedies from Catherine Daniels

In case you didn’t see yesterday’s comment that was added to Jeff Gillman’s January 6 post on home remedies, I’ve posted it here.  Dr. Catherine Daniels is WSU’s pesticide coordinator:

I’ve enjoyed reading the science-based information on your site. Keep up the good work. As regards home remedies, that is slippery slope, both legally and morally. Having a written definition of what you will or will not accept is helpful, especially if done in advance. Then you can be sure of being consistent and deliberate at least. There are both state and federal laws regarding pesticides, and state laws do vary. The most important thing is to know your state’s interpretation of those laws and to be mindful that with a blog you may be talking to people in state’s where laws are interpreted differently. I mention that for your legal protection. For example, in Washington State, if you talk to a user group (such as the public), and discuss the ways to use a material as a pesticide, it becomes a de facto pesticide recommendation. A legally-liable recommendation. When a researcher publishes information in a journal it’s not directed at a user audience so is not considered a recommendation by the author. If you take it to the public, at least here, it becomes a recommendation you made, unless you insert certain disclaimers. It’s always attractive to try and “help” the public find some easier, faster, cheaper solution to a pest problem. With pesticides and the public, you offer a better service directing them to a tested material which is registered and has a consistent concentration from batch to batch. Having personal safety and storage instructions is important…things that are missing in make-it-yourself squirt bottle solutions. Home remedies encourage people to think that the solution is “safe” (for people, not pests) because it’s made out of everyday ingredients. But as we know, the dose makes the poison. Nicotine is a nerve poison which you wouldn’t want a child to come into contact with accidentally because the squirt bottle wasn’t labelled or put in a safe place. I agree that our role is to educate, not police household cupboards or public pesticide use patterns. But by the same token, because we (educators)are trained to look at the big picture, there are good reasons to consider sticking to a label. Thanks for the opportunity to comment.

Landscape conifers: The Good, the Bad, and the Underused

This week is our annual Great Lakes Trade Expo, the main trade show and education venue for Michigan nursery and landscape industry. One of my talks was for the Arboriculture track on landscapes conifers. The theme this year was “The Good, the Bad, and the Underused.” Hey, you try giving a dozen talks a year for 10 years and see if you can come up with an original title!

 

The selections were based the following, admittedly subjective, criteria.

The Good:  These are the all-around good guys.  Conifers that are well-adapted, good growers with good form and few pest problems.

The Bad:  The problem children of the conifer world.  Pest magnets, spoiled prima donnas, or incessantly overused.

The Underused:  Trees that have the virtues of ‘The Good’ but that tend not to attract attention.

 

Here are three of my selections for each of the categories.  I’m interested in nominees from other sections of the country and the world.

 

The Good:

Eastern white pine Pinus strobus This one flirts with the overused designation but I’ll give it a nod since it’s the state tree of Michigan and figured prominently in the state’s history when Michigan was the lumbering capital of the US in the late 19th century.  A fast growing tree that improves with age.

 

Eastern hemlock Tsuga canadensis   The answer to the age-old question, ‘What conifer to you recommend for shade?’  A little finicky on site, prefers moist but well-drained – who doesn’t.  But a great elegant looking tree.  The main down side is the specter of hemlock wooly adelgid looming to our south.

 

Alaska false cypress Chamaecyparis nootkatensis (Xanthocyparis nootkatensis).  Lot of confusion over the nomenclature but no question this is a great landscape tree.  Graceful, weeping habit; good growth rate; and few pests in this area (knock on wood).

 

The Bad.

Scots pine Pinus sylvestris  Is there a pest that doesn’t affect this tree?  Our Forest Entomologist, Dr. McCullough, had a grad student count up all the pests that affect Scots pine and they lost count after 30.  Borers, tip moths, needlecasts… the hits keep coming.  The problems are exacerbated around here because of abandoned Christmas tree plantations that serve as insect breeding grounds and fungal infection courts.

 

Austrian pine Pinus nigra  Austrian pine is a frustrating tree.   In some respects it is the perfect conifer for our region. A great looking tree with dark green needles.   Good growth rate, cold hardy, drought hardy, tolerates road salt.  Everything you could want in a tree and then some.  Then the trees get about 15 years old and the wheels fall off.  Diplodia tip blight, dothistoma needle blight…  Austrian pine is the ugly duckling in reverse; looks great when young and then, blechh…

 

Colorado blue spruce  Picea pungens  The tree everyone loves to hate, yet we keep planting it.  I suppose it’s the allure of the blue that people can’t resist.  It’s like that bad boyfriend; you know he’ll do you wrong but…  He’ll lure you in with those baby blues then start hanging out with those low-life Cooley adelgids, then hook up with rhizosphaera needlecast.  And by the time the cytospora cankers start hanging out you know this relationship is going nowhere.

 

The underused

Swiss stone pine Pinus cembra  Renowned conifer aficionado ‘Chub’ Harper used to remark, “I never met a cembra I didn’t like.”  Cembras are great trees, good growers with consistently good form.  Underused but worth looking for.

 

Korean fir Abies koreana  I wrote about Korean when in discussion alternative Christmas trees but it also makes a good landscape tree.  In our area we can expect about 1’ of height growth per year.   Symmetrical form; short needles with silvery undersides, and conspicuous cones.  Lot to like about Korean fir.

 

Dawn redwood Metasequoia glyptostaboides  A fast-growing deciduous conifer with wonderful pyramidal form.  Dawn redwood is also an interesting botanical story.  Only known to science from fossil records, an isolated population was discovered in China in the 1940’s.  Seed were imported into the U.S. and the tree has been found to be broadly adapted.

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Pampas unpuzzled

Great discussion and answers on this one, gang!  Yes indeed, this is a plant out of place – as several of you noted.  But not only has it escaped from an ornamental landscape, it’s decided to grow, quite happily, in the median strip of I-5:

Another odd thing is that the species has not been officially recognized as invasive in Washington State.  It’s been languishing on the “Monitor” weed list for at least two years.  Our climate is a bit chilly for it, which may be part of the reason it looks so bad right now.  We had a very cold week back in November which may have killed this specimen back to the crown.  But never fear.  New growth will emerge this spring.  (Note to Washington State weed control board – maybe it’s time to list this plant as invasive???)

Finally, I do believe this specimen was sprayed last spring, as Jimbo pointed out.  However, it recovered and was able to send up two seed heads…which I’m sure have lavishly sprinkled the surrounding soil.