All plant samples should be submitted to the Plant Disease Clinic through your local Virginia Cooperative Extension (VCE) office.
For plant disease diagnosis and non-weedy plant or mushroom identification samples the Plant Disease Diagnostic Form (Pub #450-097) should be completed and included with the sample. Refer to instructions on preparing samples and completing the form. This form is available at your local VCE office.
Forms to be included with other sample types:
- Weed Identification, VCE publication #450-138
- Nematode Assays, VCE publications #450-901 (diagnostic), #450-098 (predictive)
- Insect Identification, VCE publication #444-113
Below is a useful video on how to submit samples to the Plant Disease Clinic. For more detailed instructions, see below.
Important: The selection and condition of the specimen and the information received on the Plant Disease Diagnostic Form are of primary importance for accurate diagnosis. A poorly selected specimen or inaccurate information may result in an erroneous diagnosis or an inappropriate control recommendation.
Complete the form to the best of your ability.
The Plant Disease Diagnostic Form was designed to accommodate a wide variety of plants and growing situations; therefore, certain entries on this form may not be appropriate for a particular specimen or situation. Whenever possible, complete this form in the presence of an Extension agent. The Extension agent can help you develop the pertinent information requested. The following explanations should help when completing the form:
- Cultivars and varieties can differ considerably in their resistance to plant parasites and adverse environmental conditions. This information is particularly important for field crops, row crops, garden vegetables, and ornamental plants.
- The area code and phone number of the Extension agent and grower must be listed. The diagnostician may be required to call the grower directly to facilitate a diagnosis.
- To avoid any misunderstanding by the diagnostician, it is essential that the problem be clearly stated. Describe the symptoms; do not write, "please diagnose the problem". Ch eck the appropriate blocks below the problem statement.
- Most of the information requested on the form helps reconstruct the "field situation" for the diagnostician. This is important since usually only a portion of the plant specimen is received by the Plant Disease Clinic. Consider each section of the form carefully; the information provides important clues to the diagnostician that are significant to both the diagnosis and the control recommendation.
- The size of the total planting and the percentage of plants affected reflect the magnitude of the problem and are important information for developing control recommendations. For field crops and row crops, estimate these figures.
- Indicate weather conditions as they pertain to the particular crop. Indicate whether or not irrigation was applied.
- Soil factors and tillage practices need to be stated where appropriate. The soil name and ASC Farm No. are optional, but should be included if known.
- If a nematode assay or soil test has been done within the last year, the date will allow the diagnostician to recover the results.
- Agrichemicals can have a profound effect on plant health and can be toxic to plants if misapplied. In addition, some pesticides, such as herbicides, may affect plant growth for more than one year after application. For this information to be of value, the chemical, rate, and date of application need to be stated.
- The last portion of the form is for woody plants such as shade trees, fruit trees, ground covers, shrubs (including those in containers), and vines. The information requested is necessary for successfully diagnosing diseases of perennial plants. Diagnosis and Control: A diagnosis and control recommendation will be offered whenever possible. It will be written primarily to the Extension agent who will relay, interpret, or modify the results, as circumstances require.
The accurate diagnosis of plant disease depends upon receiving a fresh sample. All specimens should be fresh when collected and shipped immediately. When specimens arrive unidentified, wilted, crushed, or in advanced stages of decay, accurate diagnosis is usually impossible. If the sample is in good condition, the disease will be diagnosed and acknowledged within a few days. If culturing for plant pathogens is required, or referrals to other departments are necessary, this will extend the time for results to be returned.
When possible, collect the whole diseased plant, including roots and at least one pint of moist soil. Dig (don't pull) plants with a shovel or trowel.
Collect more than one plant if various stages of decline are evident. Dead or dry plant material is of no value to the diagnostician. When possible, include healthy plants or plant parts for comparison.
Immediately after digging small plants, place the moist root ball in a plastic bag and tie the top around the stem just above the soil line. This will prevent the soil from drying during transit. Enclose the tops of the plants in a ventilated plastic bag. Do not wet the tops before packaging. When distinct spots on the leaves are the only symptoms, include several twigs with leaves still attached wrapped between dry strips of cardboard or in a thin magazine. Do not wrap leaves in wet paper towels. However, enclose a crumpled wet paper towel in the plastic bag. Do not pack this form in contact with soil.
Specimens should be packaged appropriately in a sturdy container to prevent damage in transit. Avoid exposure to high temperatures. Whenever possible, mail early in the week to avoid weekend delays in the post office.