Scout Soybean Fields for Water-Borne Diseases

May 27, 2010

WOOSTER, Ohio – Ohio soybean growers should be keeping an eye on their crop for water-borne diseases that may have cropped up during the recent heavy rains.

Anne Dorrance, an Ohio State University Extension plant pathologist, said that saturated soils and ponding conditions make it ideal for the development of diseases such as Pythium seed rot, Phytophthora root and stem rot, Fusarium root rot and Rhizoctonia stem rot.

"Right now, because of the cooler soils, the crop is most susceptible to Pythium seed rot and damping-off," said Dorrance, who also holds a research appointment with the Ohio Agricultural Research and Development Center. "We've been pulling some Pythium from our plots already."

Dorrance said that growers should scout their fields for classic signs of damage from water molds and other soil-resident pathogens.

"When scouting fields, what you'll see are big blank spaces where seedlings have died and plants haven't emerged, or plants will come up and will damp-off, meaning that they turn brown and die," said Dorrance. "If a dead plant has a red canker at the base, it's probably Rhizoctonia. If it's brown and soft, it's Pythium or Phytophthora. If it's pink, then it's probably Fusarium."

Dorrance said that in situations where growers have to replant, wait until the soil is completely dry for a few days before planting new seed.

"Pathogens tend to go dormant under dry conditions and they have to be re-wetted to get started back up again," said Dorrance. "You don't want to re-plant quickly into these fields when the pathogens are active. You may end up having to re-plant two or three times."

In addition, Dorrance highly recommends growers use seed treatments to protect the seedlings.

Despite the risk from water-borne pathogens, Ohio's soybean crop so far is in good shape, said Dorrance.

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