By Darren Hefty
Soybean Cyst Nematode, or SCN for short, is the biggest known yield robber in soybeans. Even when visual symptoms are not present above ground, the effect of a moderate SCN infestation can easily rob 10 bushels per acre in areas of your fields. For years, the best management practices you could utilize included crop rotation and planting a resistant soybean variety. However, times have changed, and so should your methods of addressing SCN if you want to raise top yields and maximize profits.
Are Resistant Varieties Still Working?
In a recent conversation on Ag PhD Radio with Dr. Jamal Faghihi of Purdue University, the data was clear. According to Dr. Faghihi, about 96 percent of soybean varieties today contain the PI88788 source of SCN resistance (otherwise known as the Fayette gene). Other sources, such as the Peking gene, are available, but hardly any varieties out there contain it as they generally have not yielded as well in either non-SCN or in SCN environments. Unfortunately, the PI88788 gene is not working as well as it once did.
What About the New Seed Treatments?
The excitement in the industry has come from the newer seed treatments. First is Votivo and its ability to repel SCN from soybean roots, providing a zone of protection. There are a number of seed treatment packages offered that contain Votivo. The yield protected by Votivo has been good, but it won’t blow you away with a crazy return on investment. Clariva is, in my observations, a little more exciting as it actually kills SCN through the season. Don’t get your expectations too high, as it won’t clean your whole fields of future SCN problems. Clariva has helped in moderate to heavy SCN areas, though, and the protection includes more than just SCN. ILeVO also seems to have good SCN activity, so the combination Bayer is promoting of Votivo/ILeVO has looked good so far in trials. If you haven’t already, start experimenting with some or all of these seed treatments, especially in your worst SCN ground.
What Other Problems Is SCN Causing?
The biggest issue in recent years in SCN fields is Sudden Death Syndrome (SDS). SCN wounds the plant, creating openings for Sudden Death Syndrome and other diseases to get inside. Treatments like Clariva and ILeVO have been reducing SDS and other diseases because they have killed or repelled nematodes.
Are SCN Populations Getting Worse?
Dr. Faghihi suggested that the populations of SCN in Indiana may be on the rise. Pat Reeg of the Iowa Soybean Association’s On Farm Network says that they have had trouble finding fields with high SCN populations in recent years due to excessive soil moisture levels. How can you know what the SCN populations are doing on your farm? The best recommendation is to test your fields for SCN every 4 or 5 years to see if your management practices are helping or leading to even more issues.
Our Recommendations
Continue using the best resistant varieties you can find. Experiment with alternate sources as they prove their yield potential and become more widely available. Utilize the seed treatment options such as Clariva or Votivo/ILeVO to help keep SCN from stealing your yields. Test your fields occasionally to monitor SCN levels. When possible, plant 2 years in a row to non-host crops to further reduce SCN populations.