Frances Gould, Morgan, Johnny W. | 8/14/2015 7:38:03 PM
Variability in Louisiana’s climate seem to be causing changes in the Louisiana population of the redbanded stink bug, said Jeff Davis, LSU entomologist.
"Redbanded stink bug is still our major stink bug pest and has been for the past 15 years," Davis said. "But last year throughout the state, there were very low populations."
In areas north of Alexandria, where winters have been relatively cold, the pest has been pushed farther south.
Davis said populations surviving the cold winter appear to be more resistant to insecticides.
"We’ve completed our action threshold research," he said. "That’s not what we’re doing anymore."
Growers are now interested in knowing whether they need to continue spraying for stink bugs even after they’ve applied harvest aid to defoliate the crop.
"When we put the harvest aid out, the growers want to know if they are past controlling for stink bugs," he said.
With soybean prices trending lower, producers need to cut expenses wherever they can. So avoiding unnecessary applications is the goal of this current study.
"What we have seen consistently throughout is a 13 percent yield loss," Davis said. "Weight is being affected, but not quality."
This means that even after applying the harvest aid, the stink bugs are still feeding on the seed and affecting weight, he said. "And when you go to the elevator, you’ll have lower test weight, which will mean lower bean yields per acre."
"It appears that redbanded stink bugs are becoming resistant to acephates," Davis said. "So we need to remind our growers to not use the same products in subsequent applications.
"Last year, we were looking for 90 percent control, but only saw 50 percent, which I consider a field control failure," he said.
With insecticide resistance becoming a problem, growers are using foliar applications of premixes that include a pyrethroid and a neonicotinoid.
Davis said the study is in its early stages and will continue for a few more years to provide conclusive results.