SCN: One cyst is the threshold for action
When sampling for SCN, attention should be paid to these areas: field entrance, along fence lines, low spots, previously flooded areas, waterfowl activity areas, high pH areas, and low yielding/stunted portions of the field. Collect 20 soil cores 6-8” deep from these areas in a zig-zag pattern using a soil probe or a spade. The soil cores should be thoroughly mixed and put in soil sample bag or a zip-lock plastic bag. Larger fields should be divided into smaller portions between 10-20 acres and each portion sampled separately. Soil samples should not be collected when soil is frozen or too wet. The soil samples should be kept at room temperature or in a cooler until shipped to the SDSU Plant Disease Diagnostic Clinic (Box 2108, SPSB 153, Plant Science Building, Brookings, SD 57007). There is no cost for SCN testing for South Dakota growers as the SCN testing is sponsored by South Dakota Soybean Research and Promotion Council.
Once SCN is detected in the soil, an integrated approach should be employed to keep the SCN numbers from building up. The first approach is crop rotation to non SCN hosts like corn, alfalfa, small grains, sunflowers, flax, and canola. For highly infested soils, longer rotations out of soybeans for several years may be necessary to bring the SCN numbers down. The second approach to SCN management is to use resistant cultivars. Resistant cultivars play two roles: 1) They are able to give high yield in SCN-infested soils and 2) they also prevent SCN numbers from increasing. The third approach is to rotate within soybean resistant cultivars. This ensures that SCN populations that can overcome a given resistance do not develop because of growing the same cultivar over and over. Other practices that promote plant health like maintaining optimum fertility, weed control (especially SCN weed hosts like pennycress and henbit), and proper drainage may increase soybean yield and limit damage by SCN. Several seed treatment products for managing SCN are available on the market but their effectiveness against SCN is still being evaluated.