Purdue University researchers have discovered that a winter weed common throughout Indiana helps soybean cyst nematode survive and reproduce, even when soybeans are not present in a field.

Purple deadnettle is a winter annual weed that usually emerges after harvest, overwinters as a seedling and fully develops in the spring. Purdue researchers discovered this fall that soybean cyst nematodes (SCN) use purple deadnettle as an alternative host for feeding and reproducing when soybeans haven’t been planted.

“SCN is the No. 1 pest problem with soybeans,” said Jamal Faghihi, Purdue research nematologist. “We are trying to understand the relationship between purple deadnettle and soybeans.”

Additional research is being done to determine if juvenile nematodes can last through the winter in the weeds’ roots.

“SCN infests purple deadnettle roots, just like they do on a susceptible soybean variety,” said Bill Johnson, a Purdue weed scientist.

Soybean cyst nematode has been detected in 82 of Indiana’s 92 counties. From 2 million to 4 million acres in the state have been affected by SCN, Johnson said. To protect soybean plants from the pest, researchers are trying to find the best timing to control purple deadnettle to reduce nematode densities.

Research supported by the Indiana Soybean Board is evaluating the impact of winter management tactics on weed and soybean cyst nematode populations in Indiana.

For now, Purdue experts offer the following strategies for reducing the SCN threat:

• Rotating crops. By regularly shifting crops, the pest’s food source is taken away. Research has shown that the nematodes still will live in the soil, but crop rotation aids in decreasing their population.

• Planting SCN-resistant soybean varieties.

• Controlling winter weeds. Like rotating crops, managing winter weeds can result in a slight reduction in nematode populations

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