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 his reason, many states have long recommended that producers periodically grow a crop of SCN-susceptible soybeans within a crop rotation when SCN populations are too low to cause yield reductions. In Kentucky, 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?" (1996). Agronomy Notes. 23.