Released September 15, 2009
BEEBE, Ark. - Continued cool, soggy weather has helped move soybean rust into 21 Arkansas counties "and the rust isn’t showing any signs of slowing down," said Scott Monfort, extension plant pathologist for the University of Arkansas Division of Agriculture.
"This year, soybean rust has proven to be more aggressive than in any other year since it first arrived into the U.S. and Arkansas," Monfort said Monday night. "This disease is more than likely in all soybean counties throughout the Delta and possibly the Arkansas River Valley. We are confident the disease will show up in many more soybean fields over the next week."
Monfort said the concentrations of the fungus are worse in river bottoms where lingering fog has encouraged further growth.
As of Monday, rust was confirmed in Arkansas, Ashley, Chicot, Craighead, Crittenden, Cross, Desha, Drew, Jackson, Jefferson, Lawrence, Lee, Lincoln, Lonoke, Monroe, Phillips, Poinsett, Prairie, Pulaski, St. Francis, and Woodruff counties.
He said all soybean growing areas of the state are at an elevated risk and growers should "take the necessary steps to protect their late soybean crop."
Growers should contact their county extension office, or see the latest soybean rust report for a checklist to help decide on whether to spray.
Growers who have already sprayed their fields at the R3 to early R4 growth stages, and are now early R5 need to be sure to scout the fields again, he said. "We have observed several fields that needed to have a second application due to disease pressure."
At R3 and R4, the soy pods near the tops of the plants are three-sixteenths to three-quarters of an inch long. At R5, the seed within the uppermost pods has grown to one-eighth of an inch.
But there’s a Catch 22. Monfort said the applications required three to four hours drying time to be effective and suggested growers "try to wait until after the rainy conditions dissipate."
Growers may be waiting a while. The National Weather Service office at North Little Rock was forecasting a 40 percent to 80 percent chance of rain through Thursday night as an area of low pressure over northeast Texas continued to rotate moisture into Arkansas.
Jeremy Ross, extension soybean agronomist for the Division of Agriculture, said that some fields that haven’t been sprayed are helping rust to spread.
"The infection is still building up there to be passed on up the road to later planted soybeans," he said.
"Growers in the Midwest have asked us to come up with a program for rust control similar to the multi-state efforts made for boll weevil eradication," Ross said. "But rust has so many hosts, like kudzu, so it would be impossible to control that way."
Five percent of the soybean crop had been harvested, according to the National Agricultural Statistics Service, compared with 3 percent last year. Eleven percent of the crop had reached maturity.
For additional information visit http://www.uaex.edu or call the soybean rust hotline toll free at 1-866-641-1847.
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http://www.uaex.edu/news/september2009/0915soyrust.htm
Writer: Elizabeth Fortune, (501) 671-2120, efortune@uaex.edu
