Soybean cyst nematode (SCN) is widely distributed in Kentucky’s soybean growing areas. The use of SCN-resistant varieties has long been a recommended production practice for infested fields. However, continuous use of such varieties can result in a shift to a race of SCN which is able to vigorously attack previously resistant varieties. For this reason, many states recommend that producers periodically grow a crop of SCN-susceptible soybeans within a crop rotation when SCN populations are at minimal levels (causing less than a 5% loss in yield). The UK Plant Pathology Department recommends a four year rotation in SCN-infested fields [PPA3; “Wanted: Soybean Cyst Nematode” (video)]. Year one should be a nonhost crop (like corn), followed by an SCN-resistant soybean variety, then another nonhost crop (corn or milo). Producers would grow an SCN-susceptible soybean variety in the fourth year of this rotation. This is, of course, provided that the three previous years have brought SCN populations down to a safe level.
Steele, Colleen C. and Grabau, Larry J., "Early Maturing Varieties and Soybean Cyst Nematodes: Will This Marriage Work?" (1997). Agronomy Notes. 27.