Wilted trees and shrubs

How to collect and submit suspect samples for vascular wilt diseases

Trees and shrubs can suffer from wilt diseases (such as Dutch elm disease, oak wilt, and Verticillium wilt). The organisms that cause wilt affect the plant’s vascular system that transports water (xylem) from the root throughout the entire plant. The pathogen’s colonization of these plant tissues blocks the movement of water, which results in the expression of wilt symptoms and the yellowing and browning of leaves.

If you suspect wilt, here are some pointers on how to collect and submit a good representative sample of your tree. Poorly collected samples and/or samples arriving in bad condition cannot be tested for wilt.

While you read the following information, please keep in mind that sample quality is critical for the success of laboratory testing and that control measures depend on proper disease diagnosis.

The Do’s for testing

Do cut live branches with symptomatic leaves. An adequate sample submission for wilt testing consists of three (3) recently wilted branches (if possible, showing vascular discoloration, see picture below) of at least 6 inches long and 1-2 inches thick.
Do place tree branches in a plastic bag to retain moisture.
Do fill out a Sample Submission Form and place it inside a separate clean bag.
Do ship overnight (FedEx preferred) or deliver samples directly to our facility.
Do contact us if you need further clarification on sample collection and/or shipping.

Sample examples — From left to right: Japanese maple branch with vascular discoloration, Adequate sample submission of 3 live branch sections of at least 6 inches long and 1 inch thick, Example of a sample shipped in a box with a completed submission form.

The Don’ts for testing

Don’t send dried up or dead branches, trunk pieces or slabs, or bark pieces. Even if the tree has wilt disease, we cannot detect the pathogen from these types of plant material. Inadequate samples can produce a false negative, which is a “negative” when in fact the tree has wilt disease.
Don’t leave the collected branches inside your vehicle as high temperatures can compromise the quality of the sample. Prior to shipping, always keep samples inside a cooler with ice packs. We highly recommend submitting samples on the same day of collection; however, samples can be refrigerated for up to 48 hours.
Don’t ship samples on Fridays; samples are not delivered to campus on weekends and may not arrive in the lab in good condition the following week.
Don’t place the sample submission form inside the bag with the plant material. Forms will get damp or soiled.

Inadequate submissions — Inadequate sample submissions. From left to right: one thin (less than 1 inch) branch section, dead trunk pieces, bark pieces, and a trunk slab.

Testing fees (per sample)

According to the place of origin, samples are charged either a $20.00 in-state or a $40.00 out-of-state basic submission fee. Pathogen-specific molecular (PCR) tests are charged an additional $25.00 fee.

Description	Total fee per sample
Oak wilt test (nested PCR for Bretziella fagacearum)	$45.00 in-state $65.00 out-of-state
Verticillium wilt test (real-time PCR for Verticillium dahliae)	$45.00 in-state $65.00 out-of-state