Serving Iowa Farmers, Keeping Nematodes At Bay

Greg Tylka’s eyes light up when he talks about microscopic roundworms. He can’t help it. Tylka finds soybean cyst nematode (SCN) biologically intriguing. The professor of plant pathology and microbiology is one of the nation’s leading experts on the pest. Even though he’s studied it for over 20 years, he says the tiny worm can still mystify him with its unpredictable ways of interacting with soybeans and other pests.

“I’m always looking forward to the next question or the next problem,” Tylka says.

It seems that SCN, estimated to infest 75 percent of soybean fields in Iowa, is always providing that next question or problem.

“The coolest thing about SCN,” Tylka says, “is that it actually changes the physiology of the soybean it attaches itself to so the plant reacts differently to other pests and organisms.”

For example, when the soybean plant is being fed upon by the soybean aphid, SCN seems to thrive, perhaps because the aphid shuts down some of the plant’s defenses. On the other hand, as nematodes

feed on soybeans, soybean aphids do not fare as well as they do on healthy plants. It’s enough to make a non-pathologist’s head spin.

Tylka and his colleagues also have found SCN breaks soybeans’ resistance to brown stem rot, and nematodes make sudden death syndrome much worse. Tylka and his team are trying to deter- mine why this is.

While Tylka has chased clues to the many riddles of SCN over the years, soybean farmers in Iowa have benefited greatly from Tylka’s work.

“I feel like I work for farmers,” Tylka says.

This is literally true. Over the course of his career, Iowa soybean farmers have funded much of his research through soybean checkoff funds.

Kirk Leeds, CEO of the Iowa Soybean Association, says Tylka is a leader as a researcher, and he takes his Extension role to heart.

“One of the most significant contributions Tylka has made to the soybean industry was in the ’90s, when he led the SCN Coalition, bringing together pathologists across the country to educate farmers about SCN and how to manage it.”

The tagline for the SCN Coalition was, “Take the test. Beat the pest.” That simple advice is still the way to keep SCN at bay: getting soil tested for the pest, growing SCN-resistant varieties and sometimes growing other crops for a year.

Tylka and his crew test hundreds of SCN-resistant soybean varieties every year—an operation he refers to as
“a well-oiled machine” that has been running for more than two decades.

He recently began evaluating new seed treatments claiming to ward off SCN. And, in 2012, farmers were reeling from the effects of the drought, but SCN was undaunted.

“SCN reproduction went crazy high. Soybean yields did not decrease, but the nematode count skyrocketed,” Tylka says. “It opens up a new set of questions I want to attack.”