Collecting the Sample
The first decision is whether to take a soil sample, a plant tissue sample, or even a water sample, or a sample of all three. Water-borne pathogens may be present in the water source itself.
- Soil Sample:
Isolation of specific fungal pathogens from the soil is often difficult due to the large number of species normally present, the presence of bacteria and actinomycetes and the seasonal nature of some fungi. Send approximately half a pint of soil representing typical problem areas. Samples should be taken to a depth of 6-8 inches. Do not sample from very wet areas, very dry areas, or from around completely dead plants. Take soil samples close to the stem of plants or trunks of trees. Try to include a sample of feeder roots also.
Place sample in either a soil sample bag or a quart-size Ziploc plastic bag. Do not place in direct sunlight or in excessively hot areas or in the freezer. Samples can be best stored at 50-58ºF for a short time. However, it is best if they are sent to the laboratory as soon as possible. Note that an assay for verticillium wilt is charged separately.
- Plant Tissue Sample:
Place woody plant material in a gallon-size Ziploc plastic bag but non-woody material in a paper bag. Do not wet aboveground parts, other than by placing between moistened paper towels if necessary, to avoid complete drying out of material. Include as much of the diseased plant as is practical. One leaf or a few needles are not enough for a diagnosis. For entire plants, retain the root system with soil in the container or plastic bag. If possible, include in a separate bag, a sample from typically healthy plants.
- Turf Sample:
Send at least a cup-cutter (6-inch) section of sod dug out from the edge of the affected area. Include any insects or grubs found when taking the sample. Place in a gallon-size Ziploc plastic bag and ship as soon as possible. Include in a separate bag, a sample from a healthy area.
- Water Sample:
A pint of water is sufficient to conduct a diagnosis. Use a clean plastic bottle and keep sample cool to retain integrity. Water may be contaminated at different times of the year. Therefore, it is a good practice to sample accordingly. Water samples are charged separately.
Any background information is most helpful in diagnosis. Poor growth may be a result of any number of factors.
- What symptoms are observed? What is the extent of the symptoms? Are leaves, fruit or limbs affected, or is the whole plant affected?
- How many plants are affected? Do the symptoms show up on only one species or on all species?
- What is the soil texture and how well does the soil drain? What is the estimated level of the water table?
- What pesticides, fertilizers or additives have recently been applied and at what rate?
- What is the source of the plants? Were they bought locally or were they imported?
- What is the age of the affected plants?
Include as much information as possible with the sample. Processing will be delayed if samples are sent separately from submittal information. Also, include payment if you do not have an established account. Ship in a sturdy box or carton. Assay results can be expected in 5-10 working days. A verticillium assay may take up to 4 weeks. Note that an assay specifically for bacteria is charged separately.
Send Sample to:
A & L Western Agricultural Laboratories, Inc.
1311 Woodland Avenue, Suite 1
Modesto, CA 95351
Phone (209) 529-4080
Fax (209) 529-4736
10220 S.W. Nimbus Ave., Bldg. K-9
Portland, OR 97223
Phone (503) 968-9225
Fax (503) 598-7702