By JEFF BURBRINK
Extension Educator, Purdue Extension Elkhart County

GOSHEN — The first time I saw soybean cyst nematode was in an irrigated field north of Middlebury in the early 1980s. The plants were yellow, stunted and seemed to follow the rows in the field. Since the pattern followed the rows for the most part, it gave the first impression that it could be herbicide injury or some other man-made problem. Since that time, we have seen SCN in many fields in the community.

I think I learned more about SCN last week than I ever thought possible. Fred Warner, who is a nematode diagnostician at Michigan State, gave an excellent talk on the subject last week at the soybean growers meeting in Shipshewana.

Warner spends a lot of time looking through a microscope, counting the tiny nematodes that have become a major issue to soybean growers. About 60 percent of the samples going through his lab have the nematode, and he is noticing a trend that is disturbing.

The primary method to limit damage to beans has been through the development of resistant varieties. The most planted lines of defense right now are PI 88788, PI 548402 (Peking), and PI 437654 (Cyst X). From Warner’s vantage point, PI 88788, the most common resistant line planted in the Midwest, may be losing its edge. In just a few short years, the SCN have begun to adapt to the traits that have made the PI 88788 line the first line of defense.

SCN is categorized by type. Type 2 SCN populations are now dominant and Warner believes growers should assume that this type exists in their fields. For the most part, Type 2 SCN is resistant to PI 88788.

Warner was disturbed by another trend. Once a grower tests for SCN and gets a positive result, there is a tendency to stop testing. Because the SCN can adapt so quickly, it will be very important for soybean growers to continue testing so they can spot trends on their own farm as the type of SCN shifts over time.