SOYBEAN CYST NEMATODE (SCN)
According to Sam Markell, NDSU Extension Plant Pathologist, Soybean Cyst Nematode (SCN) is the 2,000-pound gorilla in the room. Nationally, SCN is estimated to cause more yield loss than the next three to five most important soybean diseases. And, SCN makes diseases like sudden death syndrome (above) and brown stem rot worse.
The soybean cyst nematode (Heterodera glycines) is a parasitic worm that feeds and reproduces on soybeans, dry beans and a few weed hosts found in North Dakota. Essentially, it’s a parasite, and like any good parasite, the objective is not to ‘kill’ the host (that is somewhat counterproductive for the nematode). Rather, the nematode flourishes when it takes water and nutrients from the roots. Consequently, soybeans that are infected by SCN are difficult to detect by their above-ground symptoms. It’s not until they are experiencing yield losses of 15- 30% (or more), that they may turn yellow and/or appear stunted. You may be able to observe the white female cysts on the roots and use of a handlens and flashlight helps a lot. The cysts are much smaller than a nodule, and when young appear white to cream colored. As they age, they turn brown, and are extremely difficult to see.
The North Dakota Soybean Council supports a grower based SCN sampling program operated by NDSU Extension. Pre-labeled sampling bags will be available at local Extension offices in each county (I have not yet received them in Burke County but expect them this week).
There are three main reasons to soil sample for SCN. 1) It is the best way to identify an infected field (do you have SCN?) 2) It is the only way to quantify how bad your infestation is (how high are your egg levels?) 3) It is the best way to determine how well your management tools are working (are your egg levels changing?). Anyone interested in soil sampling for SCN can pick up to three pre-labeled SCN soil test bags from their County Extension office. The laboratory fees from SCN samples submitted though the sampling program are covered by the North Dakota Soybean Council. A total of 2,000 SCN soil test bags will be available to growers on a first come first serve basis.
As soybean acres continue to expand in the area producers need to be proactive and help survey for this pest.