Soybean growers need more than seed treatments for SCN

By Blake Jackson

Soybean growers cannot solely rely on seed treatments to combat soybean cyst nematode (SCN), according to Mandy Bish, a state plant pathologist with the University of Missouri Extension.

While seed treatments can be valuable for early-season disease protection, Bish, who also directs MU's nematode clinic, SCN Diagnostics, emphasizes the importance of soybean genetics and proper management practices in managing SCN, a major pathogen affecting soybeans in the U.S. and Canada.

In strip trials conducted at MU, the ILeVO seed treatment effectively reduced SCN in fields with high SCN populations. However, the results were inconsistent in fields with low to moderate SCN levels.

Greenhouse studies also showed that ILeVO was more effective at reducing SCN numbers compared to other treatments, though it did not completely control the nematode in either the field or greenhouse studies.

For over 30 years, the PI 88788 soybean trait has been the primary defense against SCN, with more than 95% of commercial varieties in Missouri using this resistance.

However, Bish points out that less than 5% of soybean varieties contain the Peking resistance, though its availability is increasing.

MU researchers have found that Peking-type resistance significantly reduces SCN populations, but Bish warns that it is not a "silver bullet."

In field surveys, preliminary data suggests SCN can reproduce on soybean with Peking resistance, albeit at lower levels than varieties with PI 88788. In Columbia research trials, Peking also provided a yield increase of more than 5 bushels per acre in a high-SCN environment.

"Thirty years is a long time to rely on one management tactic, and we cannot afford to use Peking soybean in the same way," Bish said.

Bish advocates for an integrated approach to SCN management, including crop rotation with corn, which is unaffected by SCN, and the use of both PI 88788 and Peking-resistant soybean varieties. She also advises farmers to conduct soil tests at the start and end of each growing season to assess SCN management strategies.

SCN Diagnostics continues to offer free SCN egg counts for Missouri soybean farmers, with support from the Missouri Soybean Merchandising Council.

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