Fond du Lac County has long enjoyed the distinction of never having a submitted soil sample test positive for soybean cyst nematode (SCN).  That changed in 2007 when at least three samples have held that distinction.  This pest is a major problem in other soybean producing states and it is likely only a matter of time before SCN reaches that status in Wisconsin.  Limiting the impact of SCN demands a keen sense of awareness and some relatively simple testing and control measures.   

        The SCN is a small plant-parasitic roundworm that attacks the roots of soybeans.  Plant damage is mainly due to the feeding of females.  The mature females are barely visible, a white dot on the soybean plant root that is much smaller than a nitrogen-fixing nodule.  The white females become yellow as they age and then brown after they die.  The brown stage is the cyst for which the soybean cyst nematode is named. Each cyst contains hundreds of eggs and are moved every way that soil moves: water, wind and farm equipment.  

Symptoms of SCN

        Symptoms of SCN infection are often patches of stunted, yellowed, less vigorous plants.  However, SCN can cause significant yield loss without causing obvious aboveground symptoms.  The only definitive symptom of SCN infection is the presence of adult female nematodes and cysts on the soybean roots.  The best method of confirming SCN is to test the soil for the presence of SCN.  These tests are offered free of charge through the UW Plant Disease Diagnostic Lab and the Wisconsin Soybean Growers Association.  Contact the UW- Extension office or your local company agronomist if you would like to have a sample taken and submitted for testing. 

        Although SCN can show-up anywhere, there are some field areas that will offer a higher likelihood for finding infections.  These include near a field entrance, areas that have been flooded at one time, areas of high soil pH (greater than 7), areas where weed control isn't quite as good, areas where the yield seemed to be a little low the last time soybeans were grown, and along fence lines where wind-blown soil accumulates.  

Management of SCN

        If SCN is detected in a field, crop rotation and resistant varieties are the foundation of a management plan.  SCN populations are significantly suppressed in fields where two or more years of a non-host crop are planted.  Examples of non-host crops include corn, small grains, and alfalfa.  In addition to crop rotation, there are soybean varieties available that offer effective resistance to SCN.