If you want to manage soybean diseases, start with the seed

ABOVE: Rows of soybeans grown on SCN-infested land frequently are slow to close or fill in with foliage. (Greg Tylka, Iowa State University)


COLUMBUS — One of the best ways to manage soybean disease is to plant the right varieties for your fields.

Seed selection is one of the most important decisions soybean farmers can make to ensure the best yield outcomes, said Ohio State University Extension soybean expert and plant pathologist Anne Dorrance.

Growers should make sure that the variety they select has the right resistance package for their field, because soybean diseases can severely reduce yields, she said.

“In the rush to plant last season, we had some fields where growers put in the wrong varieties.”

Soybean cyst nematodes

Of particular concern for the 2012 planting season is soybean cyst nematode (SCN).

SCN is always a problem for some fields because once it’s present, it doesn’t go away, Dorrance said.

Nematodes are microscopic, worm-like soil organisms that, depending on the species, can harm the growth and development of soybeans. SCN can cause substantial yield loss to susceptible soybean varieties, even when egg population densities are low and especially under dry conditions, she said.

If soybeans are going to be planted in fields with SCN, high-yielding SCN-resistant varieties should be grown, Dorrance said.

“For those folks who are managing nematodes, they need to make sure the variety has the SCN package,” she said.

If the field hasn’t been tested in a while, growers need to get it benchmarked, Dorrance said. She’s seeing some fields are creeping past the economic threshold of 5,000 SCN per cup of soil, which can result in damage.

“We’re finding that when these numbers are really high, the nematodes adapt to that resistance, so that even the resistant varieties won’t manage them.”

Dorrance said growers could check with their seed companies, which have ratings of all the seed varieties.

Other pressures

Growers can also work with their seed dealers to ensure they get the right variety for fields experiencing any type of disease pressure.

The goal is to prevent a repeat of 2009, she said, when many Ohio growers experienced a white mold outbreak after putting highly susceptible variety into fields that had long histories of having white mold that damaged yields.

“Whomever growers get their seeds from has the best literature because just about all the companies test their varieties,” Dorrance said.

Think ahead

She said the time is right for farmers to plan their seed varieties.

“Think about this now because you have the time,” Dorrance said. “In the lull while you’re getting equipment ready, now is the time to do a double check to make sure you have what you need.”

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