Research Highlights

Research Highlights
Mid-Atlantic Nematodes Overcoming Genetics

Root-knot nematodes cause round bulges, or galls, on soybean roots. Photo: University of Delaware

By Laura Temple

Nematodes, especially the soybean cyst nematode, or SCN, regularly make headlines in Midwestern ag articles — and soybean fields. Other species, like the Southern root-knot nematode, receive similar attention in the South. However, both of these nematode species and many others can be found in the sandy soils of the Mid-Atlantic region. 

“We need data to show the nematode pressure we experience in this region,” says Alyssa Koehler, assistant professor and extension specialist in plant pathology at the University of Delaware. “Farmers in Delaware, Maryland, Virginia and other Atlantic states need tools to help manage their nematode pressure, and our research is developing the case for that investment.”

Koehler led nematode survey and management research funded by the Atlantic Soybean Council. A broad regional soil sample survey in 2021 helped identify the challenges. The collaborative research continued in 2022 with a focus on understanding how those nematodes have developed tolerance to genetic resistance traits in soybeans.

Her team collected soil samples from five fields each in Delaware, Maryland and Virginia with known nematode pressure. They used a greenhouse process called HG Type testing, an abbreviation of Heterodera glycines, the scientific name for SCN. This test determines how specific nematode populations respond to all available resistant soybean genetics.

Soybean cyst nematodes. Photo: University of Delaware

“HG Typing is an alternative to race tests, and it provides a panel of lines showing how those nematodes reproduce on genetics like Peking, PI 88788, PI 90763 and four other traits,” Koehler explains. “We found results similar to other regions of the U.S. Many SCN populations have reproduction rates of more than 60 to 65% on PI 88788, the most common type of SCN-resistant genetics.”

Though these results are similar to data from the Midwest, she says the numbers reinforce the need for additional varieties with other types of SCN resistance in the high Maturity Group 3 to MG 4 range. 

“We raise soybeans from different maturity groups and with different defensive needs than farmers in the Midwest or Southern regions,” she says. “Our data reinforces the need for additional varieties that contain other types of nematode resistance.”

Seed Treatment Trials 

At the same time, Koehler’s team screened a couple seed treatments to learn about their impact on SCN populations and yield loss. Results in 2021 aligned with published data from other regions. Due to supply chain issues, they were forced to use older seed with a poor germination rate for the untreated check, so the 2022 data was inconclusive. However, she still was able to offer general observations. 

“Farmers should approach seed treatment nematicides with balanced expectations,” she says. “They do appear to offer activity against SCN to start the season, but nematodes have multiple generations during a growing season, and the seed treatment activity runs out. They are tools that can help, but there is no silver bullet.”

She adds that an additional 3 to 5 bushels of yield per acre is the high end of what these seed treatments can deliver by reducing nematode activity. 

To raise farmer awareness of nematode threats and solutions and share their findings, the team hosted two webinars and two field days, also supported by the Atlantic Soybean Council.

Additional Resources

70 Years of Progress: Fighting Soybean Cyst Nematode in North America – PDF file brochure

Alyssa Koehler profile

Published: Sep 18, 2023

The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.