Plant Disease Clinics and Diagnostic Laboratories

Latest revision: 
March 2023

Several plant disease diagnostic facilities are based in the Pacific Northwest which can help to determine the identity of pathogens involved in plant problems. Publicly supported clinics are listed below. A listing of other plant analytical facilities, both public and private, that provide testing and/or diagnostic services can be found at

For best service, and for the most useful returns on your efforts and for efficient use of our time, please read and observe these instructions before submitting specimens.

Collecting diseased specimens for diagnosis

  • Select material showing the symptoms you are concerned about. Send several samples showing various stages of disease, especially early symptoms. If possible, also send a sample of a healthy plant.
  • Get all parts of plants, including roots where practical. Enclose roots and soil in a plastic bag. Use another bag to enclose the rest of the plant.
  • If it is not practical to send the entire plant, include several affected portions of the plant. With stem or branch disorders, be sure the sample includes live material as well as the diseased portion. In other words, include the margin between healthy and diseased tissue.
  • If a vascular wilt such as Verticillium wilt or Dutch elm disease is suspected, send several branch sections that are 1 inch in diameter and about 6 inches long from branches exhibiting dying, wilted, or yellowed leaves. Do not send only dead wood. Put samples in a plastic bag to prevent drying.
  • Turfgrass samples should be taken from the edges of affected areas that include dying and also apparently healthy plants. Send one or two 3-by-3-inch squares of sod containing 1 inch of attached soil. Wrap each sample in one thickness of slightly dampened toweling, then in dry newspaper. Send as much information as possible.
  • Fleshy specimens such as mushrooms, fruit, or potatoes should be as firm as possible and show early and intermediate stages of symptom development. Wrap specimens separately in paper towels or newspaper. Do not put in plastic. Pack with sufficient padding to avoid crushing.

Packing diseased specimens for shipping

  • Keep plants cool and moist before shipping. Bag roots separately to keep soil from the rest of the plant, then enclose the entire plant in plastic to keep from drying out. Mail as soon as possible after collection. Mail specimens early in the week to avoid delay in the post office over weekends or holidays.
  • Pack in a sturdy container to prevent crushing in transit. Use packing material to securely seat the specimen in the container and to prevent the contents from moving around inside the container.
  • Identify package with labels both outside and inside. Put the label and the plant disease submission form in a waterproof plastic bag.

Addressing Packages

Oregon (from any location):

OSU Botany and Plant Pathology, attn.: OSU Plant Clinic, 2701 SW Campus Way, Corvallis OR 97331-2903
(Sample forms, fee information, directions to the OSU Plant Clinic, and other info about the OSU Plant Clinic is available at

Oregon (Northeast Oregon and North Central Oregon only):

Extension Plant Pathology Laboratory, 2121 S. First, OSU, Hermiston OR 97838 (Fees required).


Plant Diagnostics, Parma Research and Extension Center, 29603 U of I Lane, Parma ID 83660
Plant Diagnostics, Idaho Falls Research and Extension Center, 1776 Science Center Dr., Suite 205, Idaho Falls ID 83402

Western Washington:

Plant & Insect Diagnostic Lab, WSU Puyallup, 2606 West Pioneer, Puyallup WA 98371-4998 (Fees required).

Eastern Washington:

(USPS) Plant Pest Diagnostic Clinic, Dept. of Plant Pathology, PO Box 646430, Pullman WA 99164-6430 (Fees required)
(UPS and FedEx) Plant Pest Diagnostic Clinic, Dept. of Plant Pathology, 410 Dairy Road, Pullman WA 99164 (Fees required).

British Columbia:

Plant Health Laboratory, British Columbia Ministry of Agriculture and Food, 1767 Angus Campbell Rd., Abbotsford BC V3G 2M3 Canada (Fees required).

Information to accompany disease specimens

Fill out the appropriate Plant Disease Form or Plant Disease Identification Request sheets with as much information as possible. These forms are available in your county Extension offices, the labs listed above and on the web at

This information is valuable as an aid to diagnosis. Some labs will not process samples unless a form has been filled out. Photographs or even video tapes convey a lot of information that may be useful. The more information you provide, the more accurate the diagnosis will be.

Note: Neither the OSU nor the WSU clinics are allowed to accept cannabis samples (marijuana) due to university regulations. However, The OSU Plant Clinic does accept industrial hemp samples from registered growers who submit a copy of their license to grow. Additionally, the Oregon Department of Ag Plant Health can provide disease diagnostics services for both the industrial hemp and marijuana industries. Cannabis samples for diagnosis by the Oregon Department of Ag must be submitted in person by appointment only.