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

  1. 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.
  2. Do place tree branches in a plastic bag to retain moisture.
  3. Do fill out a Sample Submission Form and place it inside a separate clean bag.
  4. Do ship overnight (FedEx preferred) or deliver samples directly to our facility.
  5. 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, Samples should be shipped in a box with a completed form.

The Don’ts for testing

  1. 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.
  2. 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.
  3. 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.
  4. Don’t place the sample submission form inside the bag with the plant material. Forms will get damp or soiled.
Inadequate submissions
From left to right:Inadequate submission: One thin branch section, Inadequate submission: Dead trunk pieces, Inadequate submission: Bark pieces, Inadequate submission: Trunk slab.

Testing fees (per sample)

Description

Fee per sample

Fungal culture

$20.00

Oak wilt test (PCR)

$30.00

Verticillium wilt test (PCR)

$30.00

Ship/deliver samples directly to our facility at:

MSU Plant & Pest Diagnostics
578 Wilson Road, CIPS 107
East Lansing, MI 48824

Diagnosis process
Top to bottom: Wilt diagnosis by culturing, Sample processed for PCR.
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