Ramifications of excessive use of soybean resistance to the soybean cyst nematode, Heterodera glycines

Soybean cyst nematode (SCN) is a major prob­ lem throughout much of Iowa. Since its dis­covery in Iowa in 1978, SCN has rapidly spread throughout much of the state. It is currently a major limiting factor in soybean production. In years with adequate rainfall, yield losses due to SCN average 15 to 25%. The potential for losses of 50 to 70% or more exists in drought years