Farmers considering cover crops to help control soybean cyst nematodes need to proceed cautiously. Rotating crops and planting nematode-resistant varieties is still the best way to manage SCN.

Speaking at the North Carolina Agricultural Consultants Association annual conference Dec. 5 at the Hampton Crabtree in Raleigh, David Langston, Extension plant pathologist at Virginia Tech, said cover crops can be effective in controlling nematodes, but they must be actively managed. For the most part, grass cover crops serve as poor hosts for nematodes.

Langston said it boils down to good soil health, which leads to less plant stress. “Anything you can do to mitigate stress on the plant reduces the impact of nematode injury. You increase soil organic matter, which helps water infiltration and retention. Soil organic matter is good for nitrogen cycling, which helps the plant,” he said.

Cover crops can improve soil health, which is key to nematode management.

“When I look at cover crops, I look at it as something that’s good for the soil, building soil organic matter,” Langston said. “Soil looseners — things like tillage radishes — help improve water holding capacity. Water conservers help fight erosion. Cover crops provide nutrients and scavenge nutrients from the previous crops, and make them available for the crop you are getting ready to plant. They can suppress weeds and help control pests and diseases.”

For SCN,  cover crops as a trap can produce organisms that attack nematodes.

“Having a trap crop in the field competes with weeds, so it can suppress weed populations that support nematodes and increase soi biodiversity. Anything you can do that increases soil health and increases plant health and reduces plant stress will help. Nematodes are not going to have as much as an impact on a non-stressed plant,” Langston said.

Consider biofumigation to manage SCN, he said. Biofumigant cover crops like brassicas release compounds into the soil that suppress pests, weeds and pathogens.

When chopped and incorporated into the soil, the plant cells of biofumigant cover crops release glucosinolates, which are converted into isothiocyanates. ITCs are toxic to many soilborne pests such as nematodes.

Langston said biofumigant cover crops only work if they are actively managed. You can’t just plant a biofumigant cover crop and hope for the best.

“You’ve got to plant a cover crop in the fall. You’ve got to fertilize it. You’ve got to get biomass. In the spring, you have to chop it up; then you have to incorporate it into the soil which is not necessarily fitting that well into your no-till systems,” Langston said.