Soil sampling is helpful in diagnosing a nematode problem. Before sampling, contact the local county agent or extension specialist to determine the procedure recommended for your area. The following general procedure is recommended.
When collecting soil samples for the purpose of determining the kinds and levels of nematodes present , it is best to divide the field into units of five acres. Twenty soil cores are collected from a depth of 6 to 12 inches are collected in a systematic manner from across the area. Soil probes, which are steel tubes about 1-inch in diameter, are used to collect soil cores. The cores are thoroughly mixed and a pint of soil is bagged, labeled and submitted for analysis. When the objective of the sampling is to determine whether nematodes are responsible of plant injury in a localized area, separate samples are collected form adjacent symptomatic and non-symptomatic areas.
The time of year to sample is important. With most field crops, the best is in the fall, immediately after harvest but before tillage is conducted. Nematode populations are usually highest at this time of the year, and it is easiest to determine if a problem exists.
Nematodes are sensitive to extremes of heat and cold and drying. Samples should be kept cool, but not frozen. During sampling, keep the soil out of the sun and in an insulated container such as a ice chest. Samples should be delivered to a diagnostic lab as soon as possible. Overnight shipping is requested.