Iowa State: Soybean cyst nematodes are still a serious concern


Farmers preparing for spring planting would do well to renew their commitment to managing soybean cyst nematodes, says an Iowa State University plant pathologist.

“I’m doing everything I can to convince farmers that we are on a slow-moving train heading towards a cliff,” Greg Tylka, professor of plant pathology and microbiology, said of the push to revive a program called the SCN Coalition.

The SCN Coalition started in the 1990s to raise awareness and provide information about the yield-robbing pest of soybeans. The program was successful in getting farmers to test for soybean cyst nematodes (SCN) and take steps to manage them if they were found to be a problem.

One of the popular management techniques was planting soybean varieties that had resistance to the worm, which latches on to the plant’s roots and feeds on its fluids. Tylka said that although resistant varieties worked well, most of the resistance is based on a single genetic factor called PI 88788.

His research team has documented steady increases in SCN reproduction on soybean varieties with PI 88788 and accompanying yield decreases since 2001. Other university researchers across the country report a similar trend of increased SCN reproduction.

“Unfortunately, almost all SCN-resistant varieties available nationwide have the PI 88788 source of resistance,” Tylka said. “That’s why it’s going to take active management to lower your SCN numbers and raise your yield potential.”

The number of SCN in a field can be greatly reduced through proper management, but it is impossible to eliminate SCN from fields once it has become established, so it requires continual monitoring.

Ways to manage SCN include rotating crops, because SCN doesn’t affect corn, oats, or alfalfa; and rotating with a resistant soybean variety based on the PI 548402 breeding line, commonly known as Peking. Farmers also should consider using a seed treatment nematicide.

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