ISSUE 14 August 2, 3006
SOYBEAN CYST NEMATODE IN CASS COUNTY
A soybean field in Cass County near Argusville was recently confirmed by NDSU Plant Pathologist Berlin Nelson as being infested with soybean cyst nematode (SCN). This is the first confirmation of SCN in Cass County. The field apparently had a fairly high population of SCN, and most likely has been infested for a few years. Richland County was the first and only county in North Dakota with confirmed SCN prior to this find. Across the river in Minnesota, SCN was confirmed in Clay County for the first time this year as well. The importance of these new findings are that SCN is not limited to only one area in the state. Once established, SCN cannot be eradicated; it can only be managed. SCN is spread by the movement of infested soil, which can be moved in a variety of ways including wind, water, on implements, etc. As mentioned in the June 22nd Crop & Pest Report, the hot and dry weather may be conducive for plants to show the above-ground symptoms of SCN infection such as stunting, yellowing, and premature death. More info on SCN is included in the June 22nd article as well.
Many have asked what type of economic threshold for SCN exists. The answer is: there is no threshold. Once SCN is found in a field, the time for management practices is NOW. Although at very low populations the economic damage to soybean may be low, the reality is that on susceptible varieties, the SCN population may grow very quickly to a overwhelmingly damaging population in only one season of a susceptible variety. The keys to management are good crop rotation practices (NO MORE SOYBEAN ON SOYBEAN) and the use of adapted resistant varieties. There are currently a little more than a handful of SCN resistant varieties that are adapted to our growing conditions and maturity, but more are on the way.
If you suspect that SCN is in your field, then send soil samples from the affected areas and the margins of the affected areas to a laboratory that will test for SCN.
Carl A. Bradley
Extension Plant Pathologist