Scientists working to stop charcoal rot

UNIVERSITY OF Arkansas Division of Agriculture scientists are studying how management practices and variety selection can help producers avoid losses to charcoal rot in dryland soybean production.

“Once the plant is infected, the fungus that causes charcoal rot resides in the roots,” said John Rupe, plant pathologist for the Arkansas Agricultural Experiment Station. “It attacks when the plant is stressed by drought. Once it strikes, plants won't respond even when they get water.”

In research supported by the Soybean Promotion Board, Rupe and plant pathologists Craig Rothrock and Rick Cartwright are looking for ways to relieve drought stress on non-irrigated beans in sandy silt loam soils.

“We're trying to give producers some options that will help alleviate drought problems that lead to charcoal rot,” Rupe said. “What management practices or varieties can farmers use to grow soybeans in these conditions?”

Comparing year-to-year data is hampered by the weather. In a severe drought like the one in 2000, no practices could help fight charcoal rot. The drought itself did most of the damage. This year, Rupe said, the fields received timely rains, so the crops will have entirely different results from earlier years.

“I'd like to set up a greenhouse assay for comparison,” he said.

Even with only one year of reliable data, Rupe's work in Arkansas River Valley fields near Conway, Ark., has indicated some practices that help.

“These soils respond well to subsoiling,” he said. “Plowing deep to break the hard pan allows the soybean roots to reach deeper for moisture. There were obvious differences in plant growth between the subsoiled and non-subsoiled areas.”

He's also found that soybeans tolerate drought better when planted in 15-inch rows instead of the more common 7.5-inch rows.

“These practices won't make the problem go away, but they may reduce the damage under moderated drought conditions,” Rupe said.

He is also screening soybean cultivars for performance under conditions that favor charcoal rot.

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