A Quality Sample Is Very Important For Plant Problem Diagnosis!

An accurate diagnosis is the first and most important step of managing insects and diseases in greenhouses, fields and the home garden.

The Plant and Insect Diagnostic Clinic (PIDC) is available to all Iowans to help diagnose plant problems, identify insects, mushrooms and weed plants.  As the growing season has started, check out how to submit plant samples to the clinic.

You will find sampling and scouting tips as well as detailed information on submitting specific samples.  Not all samples are the same, so check out our different sections for field crops, fruits, vegetable and annual ornamental crops, herbaceous plants, turfgrass, weeds and woody plants

Quality digital pictures can provide important information during the diagnosis process. Check our new guidelines on how to take better pictures for Insect Diagnosis and digital photography for Plant Problem Diagnosis, Mushroom or Plant ID.  If you want to send us pictures of a physical sample you have sent us via the mail, attached you digital pictures to an email to pidc@iastate.edu and make sure to include in the subject of the email the submitter last name, crop and sample submission date (MM/DD/YY). Example: Smith-maple-05/20/15


Submitting samples for oak wilt testing

With June around the corner, brush up on oak wilt symptoms. Oak wilt symptoms occur early in June and include wilting, yellowing and/or bronzing, followed by defoliation. Oak wilt samples have to be handled with care and mail refrigerated and quickly as possible as the pathogen responsible for this disease cannot survive hot weather.


Follow this checklist when submitting samples for oak wilt testing:

  • Look for the symptoms (include wilting, yellowing and/or bronzing) and select 3 to 6 living branches from the symptomatic area in a tree.
  • Select some leaves, sending symptomatic leaves (bronzing) is a bonus, we do not test the leaves, but it gives important diagnostic information.
  • Select branches 1-2 inch in diameter (we need branches, not twigs) and 6 to 12 inches in length.  The pathogen that causes oak wilt cannot survive warm/ hot weather, if the samples are left in truck or by the house porch for as low as a couple of hours the chances of recovering the pathogen significantly decrease.
  • Refrigerate the sample, have a styrofoam chest with cold packs or ice bags. Collect the sample only when you can either deliver it directly to the PID Clinic right away or to send it overnight (never on a Friday!).
  • Follow our submission instructions on the Clinic website. 
  • Place your completed submission form in a bag, this will prevent from getting wet.

For more information about oak wilt, visit the encyclopedia entry.


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 May 22, 2015. The information contained within may not be the most current and accurate depending on when it is accessed.