2023 has arrived, and I’m already thinking ahead to the deluge of samples that are likely to arrive at the UW Plant Disease Diagnostics Clinic (PDDC) this summer.  PDDC personnel continue their efforts to balance providing high quality services to the public with keeping clinic staff and clients healthy and safe.  The following are current guidelines for submitting samples and tapping into the PDDC’s outreach programs and resources.  Our world is ever evolving, and there will likely be changes in how the PDDC functions as 2023 unfolds.  Be sure to check this document routinely for updates.

Plant Disease Diagnostics

The PDDC continues to offer digital diagnoses, and I really encourage you to submit digital photos of your plant disease problem before submitting a physical sample.  Use the PDDC online form for photo submissions.  In some situations, I will be able to provide a diagnosis and management recommendations based on your photos.  There is a $20 fee for this service.  If I cannot make a diagnosis from your photos, I will not charge the fee, but I will use the photos to provide you suggestions on what sort of physical sample to submit as a follow-up.  Note that if I charge a digital fee and you end up submitting a follow-up physical sample, the digital fee will be credited towards any lab fees for the physical sample.

You can submit physical diagnostic samples either by mail or in person.  If you opt to drop off a sample in person, PDDC staff will not likely be available for in-person consultations.  While I am committed to providing personalized service to my clients whenever possible, the PDDC is short-staffed at this time, and PDDC staff members need to concentrate their efforts on sample processing in order to keep up with incoming samples and provide timely diagnoses.

The PDDC provides an area for physical sample drop off in the hall outside the clinic.  Check for the large, black, wood shelving unit in the alcove just down the hall from the clinic door.  You can drop your sample(s) there.  Be sure to fill out a submission form to include with each sample.  You can find forms in the wall pocket to the left of the clinic door.  The form is also available online if you would like to print and fill it out ahead of time to speed up the submission process.  Please print neatly on the form and make sure to include your complete mailing address (with zip code), your phone number and your email address.  If you are a commercial client, please include the name of the business that you work for.  At this time, I am emailing virtually all reports and invoices.  If you do not have email however, just let me know, and I definitely can and will send out a hard copy of your report and invoice.

Presentations

I will be providing more in-person plant disease presentations in 2023.  However, due to the cost of traveling (both in terms of time and monetary expense), I will continue to encourage clients to consider virtual presentations (e.g., via Zoom) whenever possible and practical.  If you are interested in having me provide a presentation for a group that you are affiliated with, click here to check out a list of topics that I routinely speak on.  Email me at pddc@wisc.edu or call me at (608) 262-2863 to discuss what talk might be best suited for your audience and to schedule a date and time.

In addition in 2023, I will be sponsoring monthly Zoom presentations on a range of plant disease topics.  Click here to check out these presentations and sign up if you are interested.

Online Resources

Via the PDDC website, I will continue to provide weekly updates of my PDDC diagnoses (the Wisconsin Disease Almanac), as well as web articles (hopefully monthly, but frequency will depend on clinic sample volume).  Also check out the PDDC website for the UW Plant Disease Facts (formerly the plant disease-related titles of the University of Wisconsin Garden Facts).

I will be recording the monthly PDDC plant disease talks (mentioned above) and will eventually be working these into online playlists (with full transcripts to fulfill UW-Madison accessibility requirements) that I will make available on my nascent YouTube channel (@UWPDDC).  My Fundamentals of Plant Diseases presentation is currently available as a playlist on my YouTube channel.

Outreach teasers

I am currently working on several new outreach projects.

Limerick Book

First is my book, Limerickettsia:  A Plant Pathologist’s Book of Verse.  This is a book of 52 plant disease-related limericks with supplemental prose discussions of the diseases and original artwork.  I am in the final throes of completing this and getting it printed.  April 3, 2023 update:  Now complete!!  Click here for details.

Plant Disease Medallions

I am also working on the UW Plant Disease Facts Medallions project.  For each of the 130 fact sheets in the UW Plant Disease Facts series, I have created electronic medallions and quizzes.  Eventually, you will be able to read one of the fact sheets and take the corresponding quiz.  If you get a score of 100%, you will be emailed the corresponding medallion.  Collect them all!  Hopefully, this project will be launched to the public this winter or early spring.  April 3, 2023 update:  Now complete!!  Click here for details.

Building Block Plant Diseases

Finally, I am developing building block kits (akin to LEGO kits) of common plant diseases (with supplemental educational materials).  I have designed models for blossom end rot, powdery mildew, downy mildew of grape, apple scab, silver leaf, Armillaria root disease, and (most recently) common smut of corn.  I am now working on getting the blocks for the kits 3-D printed so that I will have prototypes available for view by this spring.  October 27, 2023 update:  The blossom end rot building block kit is set to debut in early December at the Monona Public Library courtesy of the UW-Madison Department of Plant Pathology’s graduate student outreach group, What’s Eating My Plants (WEMP).

Need information on the PDDC? 

As new PDDC resources become available, I will announce their availability via Twitter (@UWPDDC) and Facebook (@UWPDDC), or via my clinic listserv, UWPDDCLearn (email me to subscribe to this).  In addition, you can always contact me by phone at (608) 262-2863 or email at pddc@wisc.edu.

Have a great 2023 everyone!

‘Tis the Season to buy holiday gifts.  I often have a difficult time coming up with ideas for what to buy for friends and family who seem to have everything.  Similarly, I’m a frustrating person to buy for; I just have too much stuff.  If you’re trying to come up with that perfect gift, and socks, a scarf or a necktie won’t do, consider a nifty plant disease-related gift that may put a smile on a loved one’s face.  I’m not talking about a greeting card or t-shirt with a plant disease design or pithy plant disease quote but actual diseased plant materials that you can gift to a friend.

Artisan wooden bowls

There are a couple of variations on this gift idea.  If you know of someone who really loves cherry wood (me, me!!), then consider finding a local woodworker who makes bowls from burls that form on the trunks of cherry trees.  These masses of wood (galls) are often the result of a fungal infection by Apiosporina morbosa, the black knot pathogen.  When infections occur on smaller branches, I refer to this disease affectionately as poop-on-a-stick, and the galls are not of much use.  However, larger black knot trunk galls are highly prized for their amazing grain patterns and can be used to make distinctive one-of-a-kind bowls.

The other types of bowls (or other wooden art objects) that are produced from diseased trees are those exhibiting spalting.  These wooden objects are produced from trees that are suffering from wood rot (typically white rot).  These rots are fungal in nature.  As the fungus colonizes the wood and begins to degrade it, dark lines can form at the interface between healthy and diseased wood.  If caught at the right time (before substantial degradation has occurred), the diseased wood can be shaped in to stunning artisan pieces with the decorative line patterns intact.

Walking sticks

Do you have a hiker friend who needs a gift?  If so, then consider a diamond willow walking stick.  Diamond willow is not a type of willow tree, but the result of certain species of willows being infected by canker-causing fungi (in particular the fungus Valsa).  Infection leads the formation of diamond-shaped sunken areas (cankers) on affected branches.  These sunken areas exhibit a distinctive light and dark (often reddish) contrast between healthy and diseased tissue.  The diamond shapes and color combination make the infected branches highly prized for making not only walking sticks but also furniture.

Poinsettias

For a less expensive disease-related gift (the wood gifts described above can be quite pricey), consider giving a friend or loved one a poinsettia.  “What’s diseased about a poinsettia?” you may ask.  Well, the poinsettias that you buy at your local greenhouse or floral shop are infected with phytoplasmas.  Phytoplasmas are bacteria-like organisms that colonizes a plant’s food-conducting tissue.  Poinsettias, in their native habitat, are tall (we’re talking 10 ft. or more) and lanky.  The presence of phytoplasmas stunts infected poinsettia plants and makes these plants produce extra branches, thus yielding the beautiful, compact, bushy poinsettias that we have come to love.

Huitlacoche

For the gourmand on your shopping list, a can of huitlacoche (alternatively called cuitlacoche) might be the perfect stocking stuffer.  Huitlacoche is the polite name for common smut of corn.  This is a fungal disease where infection occurs through corn silks as the plants flower.  The fungus causes corn kernels to enlarge into huge, pasty gray masses (galls again).  Eventually, the interior gall tissue converts into powdery spores.  But, if you catch the galls when they are still solid and fleshy, you can use them for cooking.  Huitlacoche is a common ingredient in traditional Mexican cuisine, and many high-end restaurants now offer it on their menus.  While fresh huitlacoche is always a better choice, canned huitlacoche is readily available in specialty food stores, as well as online.

Questions?

If you have questions about any of the disease gifts discussed above, or need additional ideas for plant pathology related gardening gifts, feel free to contact the PDDC by email at pddc@wisc.edu or by phone at (608) 262-2863.  Also, feel free to check out the PDDC website (https://pddc.wisc.edu) for additional details on plant diseases and their management, as well sample submission.  You can follow the PDDC on Twitter and Facebook (@UWPDDC) or email me to subscribe to the PDDC listserv, UWPDDCLearn, to receive updates on clinic services and educational materials.

Happy Holidays and good luck with your shopping!

Note

Links in this article lead to sites that are for illustrative purposes only and are not an endorsement of any particular vendor or item for sale.

Update 12/9/22 

Here’s another plant disease gift idea I stumbled across (although there are some caveats with this one). . .

Oud perfumes and colognes 

Oud (also spelled oudh) refers to a dark, fragrant resin that is produced in the heartwood of agarwood trees (Aquilaria spp.) in response to infection by the fungus Phialophora parasitica.  Only a small percentage of agarwood trees (maybe 2%) become infected.  The combination of sap and fungus has a scent that evokes leather, saffron and smoke.  Unfortunately, oud has historically has been so valued (for a variety of purposes in addition to perfume production) that agarwood trees have been overharvested to the point where many species are endangered.  There is a move afoot to more sustainably produce oud by cultivating agarwood trees and artificially inoculating them.  So, if you decide that an oud perfume is your gift of choice, I suggest making sure the oud therein is from a sustainable source.

Update 12/14/22:  

And Santa’s plant pathology gift list grows longer (courtesy of Patty McManus, the former UW-Madison fruit pathologist) . . .

Noble rot wines 

Have a wine connoisseur who needs a holiday gift?  Then, consider noble rot wines.  These wines are produced from grapes that have been infected by Botrytis cinerea.  This fungus, if growing conditions are wet for extended periods of time, can devastate a grape crop, rotting the fruits on the vine.  However, if there is only a short wet period (which promotes infection), followed by drier conditions, the fungus causes a dehydration of the grapes without destructive decay.  This raisining of the grapes causes a concentration of sugars, and wines produced from noble rot grapes tend to be sweeter wines.  The presence of Botrytis cinerea also appears to add to the flavor profile of the wine, giving noble rot wines subtle hints of honey, beeswax and/or ginger.  Common noble rot wines include (but are not limited to) Tokaji (from Hungary/Slovania), Sauternes (from France) and Beerenauslese (from Germany/Austria).

I’ve been around long enough at the PDDC (25 years next summer) that most of the diseases that I see at the clinic are old friends.  Rhizosphaera needle cast, oak wilt, Verticillium wilt and many others are part of the cast of plant disease characters that I see in Wisconsin every year.  It’s relatively rare that I see brand new diseases.  In recent years, boxwood blight, Neopestalotiopsis leaf spot and fruit rot of strawberry and zonate leaf spot (a disease that had been on my bucket list for years) are new diseases that have crossed my doorstep.  In 2022, I’m watching for yet another new disease:  Japanese apple rust.

Japanese apple rust is a type of Gymnosporangium rust caused by the fungus Gymnosporangium yamadae.  This fungus is native to Asia (specifically China, Korea and Japan) and was first detected in the United States in Delaware and Pennsylvania in 2008 (with a first formal published report in 2009).  In 2021, Sam Fieweger of the Wisconsin Department of Agriculture, Trade and Consumer Protection (WI DATCP) Plant Industry Bureau Lab confirmed the first detection of the disease in Wisconsin.  The disease was identified on a crabapple tree in a nursery in southeast Wisconsin.

Like other Gymnosporangium rusts, Japanese apple rust is an altnernating rust.  The causal fungus requires two different host plants to complete its life cycle.  It spends half of its life on a wide range of apples/crabapples (Malus spp.) and the other half on Chinese juniper (Juniperus chinensis, Japanese garden juniper (Juniperus chinensis var. procumbens) and Sargent juniper (Juniperus chinensis var. sargentii).

Typical symptoms of Japanese apple rust are not radically different than those of other Gymnosporangium rusts.  On juniper hosts, the disease leads to the formation of relatively small branch galls that ooze orange gelatinous arms/masses in the spring.  These galls/masses look (at least to the casual observer) not that different from those produced by cedar-apple rust (CAR) and (particularly) cedar-hawthorn rust (CHR), two common Wisconsin Gymnosporangium rusts.  On apple/crabapple hosts, symptoms of Japanese apple rust are again similar to those of CAR and CHR:  large, brightly-colored leaf spots.  In the cases of CAR and CHR, the spots are yellow to orange.  In the case of Japanese apple rust, the spots are fuchsia to red.  On the undersurface of the leaves where the spots are located, short spiny structures eventually form.  These are reproductive structures that produce spores that reinfect the juniper hosts.

The presence of Japanese apple rust in Wisconsin puts a wrench in the recommendations that I typically make for managing Gymnosporangium rusts.  Chinese junipers are not great hosts for CAR, CHR and cedar-quince rust (the other common Gymnosporangium rust in Wisconsin), so I have historically recommended these junipers for clients who are desperate to grow junipers and apples, crabapples and hawthorns near one another.  If (more likely when) Japanese apple rust becomes more prevalent, Chinese junipers will no longer be a good choice to grow alongside apples and crabapples.  In the future, management of Gymnosporangium rusts will likely have to rely on not growing junipers and apples, crabapples and hawthorns anywhere near each other.

Because Gymnosporangium yamadae is not native to the US, Japanese apple rust is of regulatory importance in Wisconsin (and also elsewhere in the US).  There is interest in determining how widespread the disease may be in the state.  For that reason, I will be providing free diagnostics (as long as I am financially able – the testing is a bit pricey) for suspect Japanese apple rust samples.  The easiest hosts to verify the disease on will likely be apples or crabapples.  So, please watch for those fuchsia to red spots.  If you see anything suspicious, please submit digital photos via my online digital diagnostics form.  Let me know in the “Message” field that you suspect Japanese apple rust, and there will be no fee.  If your photos look suspicious, I’ll request a follow-up physical sample for additional lab testing.

Have questions?

If you have questions about Japanese apple rust or submitting a Japanese rust sample (or need advice about plant diseases in general), feel free to contact the PDDC by phone at (608) 262-2863 or email at pddc@wisc.edu.  Also check out the PDDC website (https://pddc.wisc.edu) for additional details on plant diseases and sample submission.  Feel free to follow the PDDC on Twitter and Facebook (@UWPDDC) or email me to subscribe to the PDDC listserv, UWPDDCLearn, to receive updates on clinic services and educational materials.

Good luck with your new workout!

Here at the Plant Disease Diagnostics Clinic (PDDC), we strive to provide the best possible diagnoses of plant disease problems.  PDDC staff use a range of techniques to do this including visual and microscopic examination of plant tissue, incubation of tissue in moist chambers to coax fungal pathogens to sporulate, culturing techniques to grow pathogens from tissue, serological tests to detect proteins specific to certain pathogens, and DNA/RNA (i.e., genetic material) detection techniques.  The PDDC’s ability to provide a high quality diagnoses using these techniques however, is dependent on receiving a high quality sample to work with.

Here are some pointers on how to provide an optimal sample so that PDDC staff can provide an accurate, timely diagnosis.

Submit a sample when you first see a problem

Diagnosing plant diseases as early as possible allows for greater flexibility in management of diseases once they are identified.  So, contact PDDC staff as soon as you see a problem.  That said, disease-causing organisms may not produce structures that we need to see to make a diagnosis (e.g., fruiting bodies, spores) early in disease development.  We may need to work with you and have you repeatedly sample and submit materials over time to accurately diagnosis your plant disease problem.

Consider submitting photos prior to a physical sample

Sometimes, we can provide a reasonably accurate diagnosis based on photos (tar spot anyone?).  If not, photos can provide useful information on the sort of physical sample that you can send to the PDDC for a more detailed analysis.  You can use the online form at https://pddc.wisc.edu/digital-diagnosis/ to submit photos.  If for some reason that form doesn’t work for you, feel free to send photos to the clinic email address (pddc@wisc.edu).  If we are able to provide a diagnosis from your photos, there will be a $20 digital diagnosis fee.  If we make a preliminary diagnosis from the photos but suggest a follow-up physical sample submission for additional testing, the $20 digital fee will be credited towards any lab fees for your follow-up sample.

When submitting a physical sample, make sure you provide the appropriate plant part

If you have any questions about what to submit, contact the PDDC for advice.  Submitting the wrong plant part can lead to an inaccurate or delayed diagnosis.

For herbaceous plants (e.g., herbaceous ornamentals, vegetables), sending in an entire plant may be the best course of action.  In some situations, symptoms that you see on the leaves of plants are an indication of a problem in the root system.  With trees and shrubs, submitting an entire plant is not practical.  For these plants, submitting subsets of leaves/needles, branches and/or roots will likely be more appropriate.

Whatever you end up sending, send A LOT.  Often, we need to perform multiple tests to diagnose a problem.  We don’t want to run short on tissue.  For leaves, send half a dozen to a dozen (or more) showing a range of symptoms.  For branches, send three or more symptomatic branches (with attached leaves or needles where appropriate).  For roots, send a large handful of the small, fibrous roots.

In particular, appropriate branch selection can be critical for accurately diagnosing vascular wilt diseases such as Dutch elm disease, oak wilt and Verticillium wilt.  For these diseases, select branches that have recently wilted/died back.  DO NOT submit branches that easily snap off.  These branches have been dead too long and cannot be accurately tested for vascular wilt pathogens.  If you suspect Verticillium wilt, select symptomatic branches from as low on the tree as possible as the pathogen that causes this disease infects through the roots.  Choose branches that are roughly one inch in diameter.  Larger diameter branches (particularly from oak trees) tend to have thick bark that is difficult to remove without contaminating underlying tissue where vascular wilt pathogens reside.  This contamination will interfere with growing pathogens from branch tissue and can also interfere with DNA-based tests for pathogen detection.  Sometimes, clients like to send in trunk sections for testing for vascular wilts.  These sorts of samples can work, but only if the trunk slices are no more that about one inch thick.  We need to be able to easily pop off the bark from these slices with minimal contamination of the wood underneath.

Submit your sample as quickly as possible to the PDDC

If possible, collect samples just before you mail them or drop them off in person.  If there is going to be a delay in submission, keep samples as cool as possible.  High temperatures can kill certain pathogens and can degrade herbaceous plant tissues, leading to what we not-so-affectionately refer to as “slime in a bag”.  Degraded samples make diagnostic testing more difficult, if not impossible.  Mail samples by overnight mail when possible.  If mailing via regular mail, please mail early in the week (Monday or Tuesday) so that samples do not sit around in a mail facility over a weekend.  Click here for details on how to package samples to make sure they arrive at the PDDC in good shape.

Help us, help you

Providing us with a high quality sample can go a long way in us providing you with a high quality diagnosis.  Let’s work together to make this happen.  If you have questions about submitting a sample (or about plant diseases in general), feel free to contact the PDDC by phone at (608) 262-2863 or email at pddc@wisc.edu.  Also check out the PDDC website (https://pddc.wisc.edu) for additional details on sample submission.  Feel free to follow the PDDC on Twitter and Facebook (@UWPDDC) or email me to subscribe to the PDDC listserv, UWPDDCLearn, to receive updates on clinic services and educational materials.

Good luck and happy plant disease sleuthing!