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College of Food, Agricultural, and Environmental Sciences


Look to Field History When Planting Soybeans

March 16, 2009

WOOSTER, Ohio -- When it comes to preparing Ohio soybeans, one of the best sources of information growers can use to make planting decisions is right beneath their feet -- the field's history.

Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, said let the field do the talking when it comes to managing two major soybean issues: soybean cyst nematode and seedling diseases.

"These problems with SCN and seedling diseases don't just occur out of nowhere," said Dorrance, who also holds an Ohio State University Extension appointment. "They slowly build up over time, so you can take your last field history, or several years of field history, and use that information to help you make a good planting decision for this season."

Dorrance said that growers with a history of soybean cyst nematode should test their fields for cyst populations and make planting decisions for resistant varieties based on the results.

Deemed the "silent robber of yields," SCN is the No. 2 soybean pest in Ohio, behind Phytophthora sojae, which causes Phytophthora root rot. Soybean cyst nematodes feed on the roots of young plants, which prevents the roots from taking up vital nutrients. The result is a drop in yields and subsequent economic losses.

The challenge, said Dorrance, is that not all resistant varieties will be completely effective against the various cyst biotypes found in Ohio.

"We are receiving more and more reports that soybean varieties with cyst resistance source PI 88788 are not performing the way we expect them to. The cyst populations are not going down when growers are planting resistant varieties. That's telling us that the nematodes are adapting," said Dorrance.

Indeed, a North Central Region soybean research project, conducted by Dorrance and her colleagues in two Ohio soybean fields last year, found that various soybean varieties originating from PI 88788 performed differently between the two fields and even within the same field.

"In Ohio, we predominantly have the SCN biotype that came in from the West, but up in the northern part of the state, we have a lot of southern biotypes. The purpose of the project was to get a handle on how these different varieties handle different sources of resistance performing under these regional cyst populations," said Dorrance. "There were certain areas of the field where resistance was not as effective and that's the concern, because where farmers rely on one source of resistance, it's not going to give them the protection they need."

Researchers plan to repeat the project again this year.

In addition to SCN, soybean growers are also faced with seedling diseases, such as Phytophthora and Pythium.

"With the cost of seed, growers can't afford to replant anymore. Treat your seed if you've ever had to replant," said Dorrance. "If producers have had a history of replant problems, where they are replanting three or four times, the first thing is to improve the drainage. Next look at your seed treatment component because just one seed treatment compound is not going to give you complete effectiveness over this whole range of diseases."

Dorrance and her colleagues recently completed a survey of 88 Ohio locations with 7,000 Pythium isolates and found that some fungicide treatments weren't 100 percent effective against the disease.

"We started digging around and identified a number of new Pythium species. We are up to 24 different species now, some are known and some are not yet described," said Dorrance. "But they all have a different sensitivity to different fungicide seed treatments."

As growers prepare for this planting season, Dorrance advises to let field history drive selecting the variety with the best resistance package for effectively managing soybeans pests and diseases.

For updates on Ohio's soybean crop as the season progresses, refer to OSU Extension's Agronomic Crops Team Web site at

The soybean is Ohio's No. 2 field crop commodity, generating nearly $2 billion to the agricultural industry, according to the Ohio Department of Agriculture. Soybeans are grown in Ohio for a wide variety of uses -- from grain to food to renewable energy production.

Candace Pollock
Anne Dorrance