Sampling for Plant-Parasitic Nematodes

Determination of nematode species and population levels can be accomplished only with a nematode assay. To be of any value, the soil sample must be representative of the site to be checked; therefore, great care should go into taking samples. Since the results of the assay are affected by the condition of the nematodes, it is also very important that samples be handled properly until they are shipped or brought to the lab. In general, the more samples that are taken from a site, the more accurate the assay will be. Large parcels of land should be divided and each unit sampled separately.

Nematode assay packets may be obtained from county extension offices or from the Penn State Fruit Research and Extension Center (FREC).

Sampling Procedure

When taking samples, follow these steps:

• If the soil in the area to be sampled is fairly uniform and the area is not very large, one composite sample will suffice. If the field is large, divide it into two or more blocks of approximately equal size and take one composite sample from each block. The sample area should not be more than one acre in size.
• In each field to be assayed, take a sample from each area that has a common cropping history and that will be planted to a single crop. For example, if a one-acre field is to be planted to peaches next year and if one-half of the field was in apples last season and the remainder in woods, collect a sample from each of the areas. If the soil in the area to be sampled is variable, such as having a heavy clay soil in one portion and a sandy soil in another portion, take one composite sample from each soil type.
• Preferably using a 1-by-12-inch sampling tube (or a trowel, small shovel, or similar tool, if a sampling tube is unavailable), take at least 20 cores of soil from each sampling area. Samples should be taken to a depth of 9 to 12 inches.
• Take soil samples from the area in which the roots were growing. Feeder roots, found at varying depths, usually are most abundant in soil at the dripline, directly below the outer leaf canopy. Do not sample from dead or nearly dead plants; rather, sample from adjacent plants.

Since nematodes generally are not uniformly distributed in a field, a carefully prescribed sampling procedure must be followed to obtain root and soil samples representative of the area surveyed. Furthermore, the samples must be properly handled and shipped to assure that they remain alive until they are processed in the laboratory. Samples can be taken any time from May to November, as long as the soil is moist and the temperature is above 40°F. If there has been a prolonged dry spell or if the soil has been saturated with water for an extended period, wait for 4 to 6 weeks of normal soil moisture conditions before sampling.

Handling Samples

• Make certain that all information requested is included on the nematode assay form that you will receive with the assay packet. This information is needed to identify the sample and to aid in interpreting assay data. If you collect more than one sample, you must assign a field number to each area sampled and place that number in the appropriate area of the form. Each plastic bag should be sealed tightly by tying it with the twist tie found in the bag. A separate assay packet must be used for each composite sample.
• Keep the samples out of direct sunlight to avoid overheating. The samples may also be damaged by heat if they are stored in the trunk of a car or other hot location. Use a Styrofoam cooler to keep the samples cool. Heat kills nematodes, and dead nematodes are unsuitable for identification.
• After completely filling out the assay forms and sealing the plastic bags, place the samples in a suitable container and send or bring them promptly to:
  
  Penn State Nematode Diagnostic Service
  Fruit Research and Extension Center
  P.O. Box 309, 290 University Drive
  Biglerville, PA 17307
  Phone: 717-677-6116
  
• A $15.00 fee is charged for each sample sent to the lab. Payment in full by check must accompany each sample. Cash cannot be accepted, and there will be no billing. Please make all checks payable to The Pennsylvania State University.

An assay report will be returned for each submitted sample, stating the numbers and kinds of important plant-parasitic nematodes that were detected. The report will also comment on the need for nematode control.