If you want to find soybean cyst nematode (SCN) in Illinois, you don't have to look hard. A 2005 study showed SCN infested 84% of Illinois soybean fields, says Terry Niblack, a University of Illinois nematologist. Forty eight percent of the fields were infested at levels above 500 eggs per cubic centimeter, the point which resistant varieties are recommended. Four percent of the fields had levels above the 10,000 eggs per cubic centimeter, the point at which SCN can overwhelm SCN resistant varieties.

Illinois bases SCN varietal resistance on type rather than race. It's based on the HG type test, an improvement over the traditional race ranking system. If your fields are infested with SCN, matching the right resistant variety with the nematode type in your field can boost profits by as much as $100 to $125 an acre.