Collecting Samples for Nematode Diagnosis
Soybean cyst nematode: To determine SCN field population levels, one quart of soil should be collected for every 10 acres. Place small quantities of soil, collected in a zig-zag pattern, in a bucket. Soil can be collected by using a sampling tube, trowel or small shovel. Soil should be obtained from the root zone, 4-6 inches, in a manner similar to that followed for soil fertility samples. If the accumulated volume of soil is greater than a quart, mix thoroughly and take a quart sub-sample for submission. SCN samples can be collected year around and regardless of the type of crop growing.
Needle nematode: In cool, wet springs, stunting of corn planted in light textured sandy soils may be caused by needle nematode. Nematode determinations for early season stunted corn should be collected before the weather turns hot. To determine whether needle nematodes are present, collect both soil and roots of stunted plants. Above ground portions of plants may be discarded. For fields with plants showing symptoms of unthrifty or poor growth (in patches with stunting, yellowing, missing plants, etc.), it may be advisable to collect two soil samples, one sample from an area in which plants are not growing well and the other from an area of the field in which plants appear normal and healthy.
Pinewood nematode: PWN causes a very rapid decline of pine. Needles, which are retained by dead trees, often have a tinge of green with a reddish brown cast to them. A sample of wood is needed to determine whether a pine tree has been killed by this nematode. A 6-8 inch long section of branch, at least 1-inch in diameter, taken from a location near the main trunk or several plugs of wood, taken with an increment borer from the trunk at breast height, are suitable for recovery of these nematodes.
Foliar nematodes: If damage by foliar nematodes is suspected, collect both healthy and abnormal leaves and place them between dry paper towels for mailing. Keep samples separate and label with identification.
Turf nematodes: Several plant parasitic nematodes can be major contributors in decline of turf, especially if ground is under other stresses. Core samples must be taken from suspected area as well as healthy turf area for comparison. Samples should not be exposed to high heat or drought.