Ok–I know something is wrong, but what is it?

Facebook and other social media attempt to help us solve problems.  This group and others seek to inform gardeners and solve problems they are having growing plants.  Looking at queries and posted responses there is so much information missing, leading to wrong and misleading comments in many of these discussions.  I think it is a good idea to reexamine the diagnostic process and how gardeners can solve their own diagnostic questions.

I know there is something wrong with this Ficus but what is it? To diagnose this tree disorder many steps need to be taken to understand the problem

Diagnosis is always the precursor to solving a plant problem. In the world of plant pathology, palliative care (treating symptoms) is often ineffective if the cause of the disorder is unknown. It is amazing how on social media so many cures, fixes, MacGyvers, or treatments are suggested even before a diagnosis is made. The diagnostic process has many components so its good to be familiar with some of the steps in this process.

Identify the plant

All plants have published names and are based on herbarium specimens. The published names of plants are all scientific binomial names. The first name is the genus and second the specific epithet or species.

Host identification comes as the first step in diagnosis. It sounds simple or silly, but knowing the host name is the first step in diagnosis. Find the scientific name of the plant and then specific disorders of that taxa can be sought out in a web search. Common names are misleading and it is critical to associate disorders with the exact plant you have a problem with. If you are diagnosing remotely (as I am often forced to do), knowing the location is the next question as many disorders are regional. For instance we don’t have black knot of plum in southern California while in southern Ontario, Canada and New York state that is a big problem.

Look at the whole organism

So many gardeners only focus on where they see symptoms. A leaf, shoot, or branch with something that does not look right is a good place to start looking, but always consider the entire plant. It is important to see the entire plant and what the distribution of above ground symptoms is. Don’t forget the “whole organism” includes its root system which is often neglected in diagnosis.

Examine the entire plant including its roots for symptoms

Look at all the components of the plant

Symptoms which are plant responses to a disease or disorder often occur on leaves. The problem, however, may be in the roots. Root rots may go undetected until almost the entire root system is decayed; only then do symptoms start to appear on the distal or far portion of the plant. These rapidly or slowly spread until the entire plant is affected. Whenever there is uniform symptomology of the foliage, always check the root system. Symptoms on only a single branch of a perennial may be localized to that branch, so follow the symptomatic branch back to its attachment point to locate any damage or disease along its stem.

Examining stems in the ficus picture above shows clear canker symptoms typical of Botryosphaeria canker in Ficus. The yellowing leaves are a symptom, but not the cause of the disorder.

Look closely

It often helps to use a hand lends to closely observe insects, insect products like webbing, eggs, pupal cases, or frass, or just to validate that there are no insects or their products present. Many many fungi form fungal fruiting bodies in dead stem portions and these look like tiny grains of pepper under a hand lens. A closer view is often helpful in deciding if a problem is localized or system in the plant.

A hand lens can supply 15-25x magnification

Look for symptoms and signs

Symptoms are plant responses to attack from pathogens, insects or abiotic causes such as herbicides, toxic salts, high and low temperatures etc. Symptoms alert the gardener that there is something wrong but may or may not point the way to the cause of the problem. It is also important to look for signs which are parts of the biology causing the problem. Fungal growths, spores, fruiting bodies insects adults and immatures stages of insects and the products they produce and leave behind are all signs. Signs give more direct evidence of the cause of a problem.

Look around

You may not be the only gardener with a plant problem. Look to see if other plants in your garden are similarly affected. If only a single taxa is affected it could possibly be a disease or insect problem. If many different kinds of plants are affected it may be from a non-biological cause–an abiotic disease or environmental disorder. Solving these diagnoses often requires lab work and specific soil or plant sampling

Distortion of new growth is a symptom. it has many causes but the fact that it is occurring on multiple taxa in a single site suggests herbicide toxicity. In this case the culprit is an herbicide called Polaris and the active ingredient is imazapyr.

Seek confirmation

Once you have collected all the the information (symptoms and signs) over the entire plant (including if necessary root symptoms), it is time to put the information to work. Searching on your own, on the internet, is daunting because there is so much misleading information. If you have the scientific name, you can put that in a search engine along with the symptoms and tentative ID of insects or pathogens and then look at all the images that match what you have. Click on the image and check the source of the file. If from an .edu or educational source, it is likely a higher quality of information. Read these first.

Taking samples to a lab or University Extension office is of limited value because they can’t see the entire plant. It’s best to take samples to an expert when you have a good hunch what is going on and you want to confirm it (you should include images of the whole plant if you can). So much money is spent sending random leaf or twig samples to labs and they end up sending information that is misleading or just wrong as far as the diagnosis goes. Thousands of fungi grow on plant surfaces and labs will isolate these, some are pathogens but may not be on your specific plant as pathogens can be quite specific to plants they have a disease relationship with. The lab report comes back with a finding Alternaria spp. This is indeed a pathogen of tomato and many other plants but it is also a very common saprophyte often found growing on dead plant tissues. So lab findings are helpful when they confirm your own suspicions, but often unhelpful when random plant tissues are sent by a gardener that has no idea what is happening. This is true of any lab, university or private. The more information the lab has, the more helpful they can be. And all labs everywhere would prefer to have the entire organism for diagnosis.

Diagnosis is hard. The best diagnosticians are correct (solve the diagnostic problem) about 2/3 of the time. Sometimes diagnosis of a problem can take years. Some diagnoses are never solved. But for most common plant problems you can find answers by intelligently searching the internet and with some help from the “ologists” of University and private diagnostic firms.

This disorder of Lantana camara took over ten years to diagnose. Samples sent to the state agriculture lab were studied for virus and fungal pests. No results came of it. The disorder was finally resolved when flies of the genus Liriomyza spp. were reared from leaves. Lantana Blotch Miner is widely distributed in Southern California only on L. camara.

Published by

Jim Downer

Dr. Downer has 34 years of experience as a horticulture and plant pathology Advisor with the University of California Cooperative Extension in Ventura County. Dr. Downer’s academic training is from California Polytechnic Univ., Pomona, (BSc. horticulture & botany, 1981; MSc. Biology, 1983;. In 1998 he earned a Ph.D. in plant pathology, from University of California, Riverside. Dr. Downer’s research is focused on mulch, soil microbiology and disease suppression in mulched soils, diseases of shade trees and cultural practices to maintain landscape plants. Dr. Downer is a member of the American Society of Horticultural Science, the American Phytopathological Society, The International Soc. of Arboriculture, and the Western Chapter of the ISA, and the International Society for Horticultural Science. Dr. Downer is an Adjunct professor at California Polytechnic University in Pomona. Dr. Downer serves on the Board of the John Britton Fund for tree Research as the chair of the research advisory committee, and currently chairs the regional conference committee for WCISA. Dr. Downer has a love of shade trees, Shinrin roku (forest bathing/walking) tree work, wood working, horses, gardening, horticulture and the study of plants and their biology.

4 thoughts on “Ok–I know something is wrong, but what is it?”

  1. When I am working in a booth for master gardeners, I have suggested that a sample be accopanied by at least three photos: 1) The plant the in its environment so that we can see what is around it. 2) the entire plant close up. 3) a close up of the problem. More (within limits!) are better. This won’t always work, but it is a lot more helpful than just a sample, and most people have cell phones that take good photos.

  2. I am with Cherie 100% on this one. Also, I find it useful when searching the internet to include in the search window the letters of a local university (for example, here in Washington state: “Fusarium solani wsu). This helps eliminate a lot of junk and helps localize response information.

  3. Great article and great comments, this will certainaly help me a lot at work. “All the leaves are falling off” is a common description from customers. We only have a 3-month return policy on trees and shrubs at our nursery but it’s surprising how often people want a replacement when the plant has been left in its pot and not watered! No diagnosis needed…

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