Soybean Cyst Nematodes have long held the position as one of the largest yield robbers of soybeans in the United States. They aren’t giving up that position without a fight. Many soybean cyst nematodes have figured out how to feed on and reproduce on soybean varieties that have genetic resistance to SCN. This has been documented in Michigan as well as many other Midwestern states.
As soybean growers have confirmed the presence of SCN on their farms, most of them have turned to the most effective management option which is genetic resistance. The use of resistant varieties and careful crop rotations has been successful in lowering SCN populations and increasing soybean yields for many years. But SCN soil sample analysis is showing an increase of SCN populations in some fields even where resistant varieties are being used. One of the reasons for this issue is the fact that nearly all of the commercially available soybean varieties that are resistant to SCN have their genetic source of resistance from one line, PI88788. This tool has been used on as many as 8 –10 soybean crops over the last 15 – 20 years within a field.
A soil sample program to evaluate SCN populations across Michigan in 2015 showed that several fields contain SCN which are reproducing on resistant soybean varieties, especially with the most common resistance source, PI88788. One of the samples showed that the nematodes in that field reproduced 73% as well on the PI88788 resistance as they did on a susceptible variety. Additionally, that same field showed 29% reproduction on a Peking variety as on a susceptible. This sample does not represent an average or normal population but does indicate the trend of significant shifts of SCN populations.
This analysis is called type testing and is available at MSU diagnostic services along with a general SCN population analysis. The Michigan Soybean Promotion Committee has allocated funds to cover the cost of both the SCN population analysis and type testing. You can access an SCN sample form on the MSPC website, www.michigansoybean.org, or by calling the office at 989.652.3294.
This information is provided by soybean farmers through the MSPC – the soybean checkoff. For information about the MSPC, visit www.michigansoybean.org. MSPC delivers educational information to and on behalf of Michigan’s soybean farmers.