SCN Detection and Host Crops

By Dusty Sonnenberg, CCA, Field Leader, a project of the Ohio Soybean Council and Soybean check-off

Soybean Growers in Ohio are encouraged to pull soil samples to submit for Soybean Cyst Nematode (SCN) analysis this fall. Soybean Cyst Nematode is the number one yield robber of soybeans in North America with yield losses of up to 30% possible.  Dr. Horacio Lopez-Nicora, Plant Pathologist and Nematologist at The Ohio State University said that their lab is processing up to two samples free of charge for every Ohio farm with support from the Ohio Soybean Council and Soybean Check-off.  When the samples are received, they will be processed to see if a SCN is present, and also the number of eggs to understand the level of infestation.

It is important to know not just if SCN is present, but also the level and type. “One thing that we are really promoting is to know your numbers of SCN,” said Lopez-Nicora. “Sample your field, know if you have SCN, and how much. We also need to know what type of SCN we have in the field. Unfortunately, the SCN population in Ohio is one that can overcome a specific source of resistance, PI 88788. This source of resistance is present in over 90% of the commercially available soybeans in Ohio. This means that our SNC population can overcome, adapt and reproduce on PI 88788.”

Once the sample analysis is received, a grower can make the appropriate management decisions. “If this PI 88788 SCN resistant population is what is in your field, then a different source of resistance should be selected to protect the soybean crop,” said Lopez-Nicora. “There are cultivars or varieties that have a different form of resistance that can be selected. The use of seed treatments is also beneficial.”

“When managing SCN we follow the 3-R’s,” said Lopez-Nicora. “Rotate, Rotate, and Rotate. Rotate to a non-host crop such as corn or another non-host crop that the SCN cannot reproduce on. If you go back to soybeans, select a variety with a different form of resistance. If you repeat planting soybeans, rotate varieties. Don’t train the nematodes to feed on the same genetic material. Finally rotate sources of resistance. If we start rotating and not using the same source of resistance, we will avoid the selection pressure of the nematode.”

Understanding which plants are host plants for SCN is important. Certain weeds and some cover crops can serve as a host crop for SCN. “We are studying which weeds serve as a host to SCN,” said Lopez-Nicora. “Purple Deadnettle and Henbit are two that SCN can survive on and complete their life cycle and reproduce. You need to pay attention to what is going on at the end of the season in your fields. If we don’t take care of the weeds present with a fall burndown herbicide application, those could host and support the SCN.”

The incorporation of cover crops in a rotation has gained popularity in recent years. While cover crops provide many benefits, selecting the wrong cover crop could unintentionally increase SCN populations in a field. “Field Pennycress is being pushed to be grown in some areas as an alternative crop or cover crop, but we know that this particular plant will allow SCN to reproduce,” said Lopez-Nicora. “If a grower has a field known to have SCN present, then pennycress is a plant that they would not want to include in a cover crop mix or rotation.”

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