Soybean Cyst Nematode: Crop impact
Soybean cyst nematode (SCN) silently robs significant soybean yield without displaying obvious above ground symptoms. Unfortunately, when SCN is introduced in the field, it can never be completely eliminated; however, SCN can be managed to keep SCN population below injury level. By the time one soybean cyst is observed on the soybean roots or in the soil sample, likely more cysts are occurring in that field. One cyst can contain up to 300 eggs, and 2-3 cyst cycles can occur in a growing season.
SCN management starts with a soil test to determine the presence or absence of this nematode in the soil. Absence may indicate that either the soybean cyst nematode has not established in the field or it could be present at non-detectable levels. Therefore, there is a need to keep testing the soil every so often (recommended every three years). A positive SCN detection requires adoption of an integrated management approach that includes planting resistant cultivars, crop rotation with non-hosts, and use of nematicide seed treatments especially for fields where SCN egg counts are very high (>10,000 eggs/100 cc of soil). It should be noted that the effectiveness of nematicide seed treatments has not been consistent across the region.
Sampling Soil for SCN
When to Sample: Soil sampling for SCN can occur at any time throughout the year as long as the soil is not completely saturated or frozen. If you were unable to get your fields sampled for SCN this fall, consider sampling this spring.
Areas to Target When Sampling: Field entrance, along fence lines, low spots, previously flooded areas, waterfowl activity areas, high pH areas, and low yielding/stunted areas of the field.
How to Sample: Collect 20 soil cores 0-6” deep in a zig-zag pattern using a soil probe (Figure 1) or a spade. The soil cores should be thoroughly mixed and put in a soil sample bag or plastic bag (only about a pint is needed for testing). Larger fields should be divided into smaller 10-20 acre field portions, and each portion sampled separately.
Storage & Delivery: Make sure you fill out an information sheet for each soil sample bag submitted. Soil samples should be kept at room temperature or in a cooler until shipped/delivered to the SDSU Plant Diagnostic Clinic.
Cost: There is no cost for SCN testing for South Dakota growers. SCN testing is sponsored by South Dakota Soybean Research and Promotion Council.