Johnny Morgan, Davis, Jeff A. | 7/8/2015 11:21:31 PM
BATON ROUGE, La. – LSU AgCenter researchers are looking at different aspects of the redbanded stink bug.
Changes in the state’s climate seem to be causing changes in the population of this insect in Louisiana, LSU entomologist Jeff Davis said.
“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 further south.
Davis said as populations that are surviving the cold winter appear to be more resistant to insecticides.
“We’ve done our 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 their 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. Not in volume, but in weight.
“I never would have thought it was that important, but it is,” he said. “Weight is being affected, but not quality.”
This means that even after applying the harvest aid, the stink bugs are still sucking on the beans and affecting weight, he said. “And when you go to the elevator, you’ll have lower test weight, which will mean lower beans 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 the same tank mix.”
“Last year, we were looking for 90 percent control, but only saw 50 percent, which I consider field failure,” he said.
With resistance becoming a problem, growers are using foliar applications of premixes which include a pyrethroid and a neonicotinoid. The neonicotinoid products came on the market in the late 1990s.
“As some people like the kick from nicotine, so is the effect on insects,” Davis said. “You can actually sometimes see them shake as their nerves fire from being exposed to the nicotine.”
These chemicals have been very effective in Irish potatoes. They are providing control for the Colorado potato beetle, and they are great for aphid control, he said.
Neonicotinoids can be used from the time the plant is put in the ground, Davis said.
The redbanded stink bug is a semitropical species that really does not like the cold. So when the temperature drops below 20 degrees, you really start to see an effect on their mortality, he said.
Davis said the study is in its early stages and will continue for a few more years for conclusive results.