Soybean Disease Could Indicate More Serious Problems

August 27, 2002

WOOSTER, Ohio - A relatively new soybean disease to Ohio is being used as a bio-indicator to diagnose a more serious economic problem.

Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, said some soybean plants in Ohio are suffering from sudden death syndrome (SDS) - a fungal disease that causes root rot and crown rot and eventually kills the plant. So far in Ohio, every SDS field has experienced problems with soybean cyst nematode (SCN).

"For every field where we are finding SDS, we are also finding high cyst populations. There has been some type of association between the two," said Dorrance. "So we are urging farmers to manage soybean cyst nematode. You manage the pest, you manage the disease - reason being that soybean cyst nematode will cause more economic damage on the crop over time than SDS will." SDS has only been present in Ohio for about six years, but is slowly popping up in more areas throughout the state. Symptoms are characterized by bright yellow spots on the leaves, with older leaves exhibiting necrotic areas between the veins. About two weeks before normal maturity, the plant will lose its leaves and die. Some of the factors that favor disease development include heavy rains during the vegetative growth period prior to flowering.

Dorrance said that SDS is also associated with poor soil drainage and the majority of the plants being affected are growing near roadsides and field edges where drainage is inadequate.

"Growers can help manage the disease by improving soil drainage in their fields. Soybean varieties also exist that show resistance to SDS. Good cultural practices are important in managing SDS," said Dorrance, re-emphasizing the need to control for soybean cyst nematode.

"I've said it before and I'll say it again, the best way to manage soybean cyst nematode is crop rotation, crop rotation, crop rotation," she said. "And also plant resistant varieties. Soybean cyst nematode can be present in a field without SDS, but we are using SDS as a bio-indicator for the presence of cyst populations." Though researchers have yet to determine the association between SDS and SCN, one theory is that cyst feeding on the plant roots weakens the plant and creates wounds from which the fungus can enter.

Dorrance speculates that SDS will continue to spread in the face of high SCN populations and continuous soybean plantings. So far this year, approximately 600 soybean acres are infected with SDS.

Author(s): 
Candace Pollock
Source(s): 
Anne Dorrance