Plant and Insect Diagnostic Clinic - 2018 Year in Review!

My favorite cases this year were redbud and peach trees, both had signs of winter injury, and two fungal pathogens were tagging along, Botryosphaeria causing cankers (in redbud) and the fungal wood rot caused by Schizophyllum commune on both peach and redbud. These cases are fascinating, the cold injury happened first and the savvy pathogens come to join the party!

Schizophyllum commune fruiting bodies, produced in the lab
Schizophyllum commune fruiting bodies, produced in the lab.

In my list of favorites Phytophthora causing root rot in mandevilla, the foliar (blight) symptoms on this flowering vines may be misleading because the pathogen is causing the damage in the roots!  Also, check out the samples I received with the coolest fungal structures (signs)  orange rust in blackberry, and flag smut in turf, it was my first time seeing them in-person and it is so much better than pictures in a textbook. 

This past season we received multiple samples and inquiries from clients wondering if their plants may be suffering from verticillium wilt (see encyclopedia article –verticillium wilt), a vascular pathogen that can cause disease in many plants. To properly test for this pathogen, the sample type is very particular, see our instructions for submitting woody plants, section "suspect a wilt problem?" Other problems may resemble the symptom Verticillium may cause, including cankers, drought, root problems, decline or poor site or environmental conditions. Testing for verticillium wilt is critical as it will help you decide what to replant and how to treat any dead plants.  Verticillium can remain in the plant tissue so it is very important not add infested plants  to your compost pile or us mulch from an infested tree.  Verticillium will also remain in the soil even after a the infected plant is removed so you will need to replant with a resistant variety.  Here is a list of plants not susceptible to verticillium wilt that you can use in infested sites. 

Other common samples were oak wilt, trees and woody ornamentals with fungal cankers and various fungi causing leaf spots. We received multiples cases of Stigmina needle blight on spruce trees; two-lined chestnut borers in oaks and trees with physiological leaf scorch.

Schizophyllum commune on a peach tree.
Schizophyllum commune fruiting bodies.

We also evaluated many samples for potential herbicides injury symptoms. Our evaluations of herbicide damage are based on a visual inspection of symptoms combined with information provided about products the plants may have been exposed to, and when symptoms appeared.  We do not test for herbicide residue in our laboratory.  We can also rule out possible diseases that can have symptoms that resemble chemical injury.  For more information on steps you can take to limit chemical injury to you r plants please see our article Preventing Herbicide Injury in the Landscape. Often, the source of the chemical may be inadvertently contaminating the garden and causing symptoms, see our article Chemical Injury in Vegetables

Thank you for your continued support and patience throughout the year as we transitioned from our old home to our new clinic space. We can’t wait to show you the new facilities and break in the new gear.  We look forward to serving you and helping you keep plants healthy next year and hope to see you in our workshops or presentations in 2019!!

PID Clinic HOLIDAY HOURS: the Plant and Insect Diagnostics Clinic will be observing the University holidays and will be closed December 24-25, January 1, 2019. 

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on December 14, 2018. The information contained within may not be the most current and accurate depending on when it is accessed.