Guidelines for Collecting Plant Samples for Disease Diagnosis
If you are submitting a plant sample for diagnosis, please note that:
- A single plant sample may not be enough, such as for leaf and fruit diseases. Several plant/leaf/fruit samples showing a range of symptoms and present at various stages of disease development will be needed for accurate diagnosis. In short, choose samples that demonstrate the early, middle, and late stages of disease progression.
- The sample(s) should be representative of the overall plant population in the field.
- Dead or dying tissues should not be sampled. If sending a stem sample, check for green tissue underneath the bark.
- Do not collect leaf or plant samples that are heavily covered with soil or dust.
- Do not collect samples from plants that are damaged by insects, animals, agricultural equipment, etc.
- Sampling is not recommended when plants are under moisture or temperature stress.
- Stem and branch specimens should be at least 8 to 12 inches long, and should include the disease area as well as part of the healthy area.
- For plants showing wilting, yellowing, stunting, or general decline, collect the entire plant, including the root stem. Plants should be carefully dug from the ground—not pulled out—so that the root system remains relatively intact, but be sure to shake away any excess soil. Enclose the root system in a plastic bag, while placing the rest of the plant sample in another plastic bag.
- Be sure that root samples are from affected plants, and not from adjacent weeds.
- For lawn and turf diseases, submit a 3 to 4 inch diameter plug containing both diseased and healthy turf tissue.
- Do not add any additional moisture to samples.
Guidelines for Submitting Soil Samples for Disease Diagnosis
If you are submitting a soil sample for disease diagnosis, please note that:
- Using a hand shovel, scrape away surface litter, and remove the top 3 to 5 inches of soil.
- Avoid taking samples from areas such as lime piles, fertilizer spills or bands, livestock congregation areas, poorly drained areas, dead furrows, and areas close to roads or pathways.
- Do not sample especially dry or wet soil.
- Take soil close to the rhizosphere (root) zones of affected plants.
- If collecting soil from multiple sites as a composite, mix in a clean plastic bucket, and send a total of approximately 500 grams (1.1 pounds) of soil.
Sample Submittal Forms
You can fill out the sample submittal form online, or print and fill out a hard copy to send. See the following forms:
Your samples should also be accompanied by several important permits and pieces of documentation:
- Include this permit if you are shipping samples from within the US EXCEPT California: US Permit
- Include this permit if you are shipping samples from OUTSIDE the US: International Permit
- Include this permit if you are shipping samples within CALIFORNIA: California Permit
- W-9 Form
- Shipping Label
Questions? See the guidelines on soil and tissue sampling above, or download a PDF copy of our sampling instructions.