Collecting the Sample
“How will I use the assay results?” is the most important decision about when and how to sample a field for plant parasitic nematodes. Instructions for four of the most common scenarios are detailed below:
Poor root growth – stunting, swelling, discoloration
Abnormal foliage – stunting, discoloration, canopy is slow to close
Collect soil and plant samples early in the season at the periphery of the zone where symptoms occur. Bulk soil cores into one bag and include several plants (entire plants if they are small or roots only for larger plants).
Information to include with the sample: cropping history and a description of symptoms including how long symptoms have occurred and the pattern of problem areas in the field.
Evaluate a seed treatment for the current crop:
Collect plant samples about 30 days after emergence. Carefully dig multiple plants taking care not to break roots. Do not clean the roots – it is best to leave some soil surrounding the root mass. Place samples collected from nontreated zones in a separate bag.
Information to include with the sample: crop, product used and clear instructions that the assay is for product evaluation – this is particularly important if a soil assay is requested.
Diagnose a field consistently falling short of its yield potential but with no apparent symptoms of nematode damage
Select a cultivar or seed treatment for the next crop:
Collect samples from each management zone using a zig-zag pattern for soil sampling. More cores are better and if the size of the sample is a concern the cores can be broken up, thoroughly mixed, and subsampled for submission. Cores should be collected to a depth of 6 to 9 inches. Plants do not need to be included. Samples collected before July will have predictive value for the current crop. Samples collected after July will not provide information reliable for the current crop, but are valuable for determining if nematodes are the likely cause of an on-going problem. Assays for nematodes can be performed year-round providing a number of cores are collected.
Information to include with the sample: cropping history and a description of the problem.
Handling and Submitting the Sample:
Only live nematodes are recovered by some of the assays we use, so improper handling procedures can compromise the information you receive. Avoid placing samples in areas warmer than 78 degrees: place bags in the shade in the field and store indoors at room temperature or cooler. Do not throw, shake, or agitate samples. If mixing cores to collect a subsample, stir the soil gently but thoroughly. Use a bag or container that will keep samples moist.
We assay about a pint of soil so the sample may be reduced in size before sending.
Send or deliver samples to:
Nematode Diagnostic Lab
University of Wisconsin
1630 Linden Drive
Attention: Dr. Ann MacGuidwin