Vascular wilts testing

Observe symptoms and patterns, document what you see with pictures while inspecting the plant.  Visit our Digital Photography page for some guidelines and how to share photos with us.

Follow our guidelines for examining unhealthy trees at the resource Identifying Tree Problems (free pdf)

Collect samples from branches that are showing symptoms but are not dead. Include twig with leaves too. Download and fil submission form.

Dutch elm disease and Verticillium wilt testing:

Branch specimens should consist of 4 to 6 pieces, measuring 6 to 8 inches long, and 1/2 to 1 inch in diameter (verticillium wilt) and at least 1/2-inch thick  (Dutch elm disease). Check for vascular discoloration when collecting samples and include branches with sapwood discoloration. 

Suspected oak wilt samples:

Check our video below and use our oak wilt sampling checklist here

Download a printable checklist and submission form

Check out our short video below and follow the forest service guidelines at this page.  In brief:                                                                        

Oak wilt packaging example.
Oak wilt packaging example. (Top left) sapwood discoloration. (Top right and middle) symptomatic leaves. (Bottom pictures) note the icepack (red arrows) on each side of the branches in the bag. Note submission form filled and enclosed in a separate bag.

  • Collect the sample only when you can either deliver it directly to the Clinic or to send it overnight (never send on a Friday!).
  • Prepare a styrofoam or plastic chest and ice packs (see example in next page). Refrigerate the sample (from collection to delivery). The pathogen that causes oak wilt cannot survive in hot weather. If the samples are left in the truck or by the house porch for as few as a couple of hours the chances of recovering the pathogen significantly decrease.
  • Observe symptoms, look for the symptoms (wilting, yellowing and/or bronzing).
  • Select branches where symptoms are developing. Collect 3 to 6 living branches from the symptomatic area in a tree. Branches should be at least 1/2 in diameter and 6 to 8 inches in length (we need branches, not twigs).  With a knife peel the bark and inspect for vascular discoloration. When discoloration found, collect additional branches from that symptomatic limb.
  • Avoid sending dead branches.
  • Select some leaves, sending symptomatic leaves (bronzing), it gives important diagnostic information.
  • Place your completed submission form in a bag to prevent it from getting wet.
  • Ship the package early in the week via overnight delivery. Do not send on a Friday. Walk-ins are welcome!

Send the samples overnight and include ice in the packets around the sample (see photo,  important for oak wilt testing). Refrigeration is crucial, lack of refrigeration increases the chance of false negatives.  

Additional tests available

Please note, to request the services below, use the box on our form titled “I give my approval for additional testing fees. (Plant problem diagnosis ONLY)”. We also recommend contacting us prior to submitting a sample for serological testing to ensure that we have the supplies on hand 

Perform DNA testing 

Oak wilt (Only offered between June- October 1st). Cost: additional $30+ Standard fee $20, total cost $50  *Time to result: 10 business days. *follow instructions for oak wilt sampling. Especially recommended for oaks in the white oak group (lobed leaves), and all oaks after mid-September. This service needs to be performed at sample arrival. 

Send the samples overnight and include ice in the packets around the sample (see photo, important for oak wilt testing). Refrigeration is crucial, lack of refrigeration increases the chance of false negatives.