Collect Whole Plants When Possible
Often growers first realize that they have a plant disease problem when they notice abnormalities in their plants’ growth above ground. However, many times symptoms observed above ground are an indication of something going wrong below the soil surface. Therefore, samples that include whole plants are more likely to provide the information needed for PDDC staff to make a proper diagnosis.
Always Dig, Never Pull Plants
Often diseased root tissue or pathogen structures associated with roots are very delicate. Pulling plants from the soil may shear diseased tissue or pathogens away, making diagnosis more difficult.
Collect More Than One Plant
Diagnosis of a plant disease often involves performing several tests on a sample. Sending more than one symptomatic plant ensures that there is sufficient plant tissue for all of the required tests.
Collect Plants That Show a Range of Symptoms
Diagnosis may involve looking for pathogen structures (e.g., fungal reproductive structures) that may be formed only at certain stages of disease development. Providing a sample of plants showing a range of symptoms may speed diagnosis by providing tissue with these structures. Including healthy plants with your diseased plant sample can help in detecting subtle symptoms in diseased plants.
Keep Collected Plants as Fresh as Possible
Disease problems on fresh plants are more easily diagnosed than those on plants that have wilted or rotted prior to their arival at the PDDC. If possible, collect plants immediately before they are to be mailed or brought into the PDDC. If there will be a delay betweeen the time that plants are sampled and their arrival at the PDDC, keep the plants cool. Plants collected from home gardens can be kept in your refrigerator. Plants collected in a remote location should be placed in a cooler with ice.
* DO NOT * place samples on your car or truck dashboard as they can overheat and deteriorate very rapidly.
Keep Foliage From Becoming Contaminated with Soil
Wash roots gently to remove soil unless the sample is to be tested for nematodes or you are submitting a potted plant. Soil contains many microorganisms that can readily colonize dead or dying tissue. These microorganisms (called saprophytes) can interfere with our ability to recover pathogens from diseased tissue. When removing soil from roots, do not scrub the roots as this can lead to the loss of root tissue that may be important in disease diagnosis.
Collect Other Important Information
The diagnosis process often involves piecing together many different clues. Background information is crucial. When submitting a sample, include information about:
- the plant (name, variety, age)
- symptoms (unusual plant size, color or shape, severity of the disease)
- the environment (weather patterns just prior to the onset of disease symptoms, soil type where the plants are growing, amount of water that the plant has received, and the amount of sun or shade that the plants receive)
- management factors (previous crops, fertilizers and pesticides that you have used, pesticides used by your neighbors (if known)).