Insect pests’ impact on soybean plants, other crops studied

Mild winters are nice and welcomed, but the insects they bring are not. Stink bugs, especially the redbanded stink bug, do well when the temperatures stay in the mild range through the winter months.

LSU AgCenter entomologist Jeff Davis said he found stink bugs in agricultural fields earlier this year than expected.

In a normal year, the redbanded stinkbug is found in clover until early summer, and then they move into soybean fields.

Davis is also monitoring insect pests for insecticide resistance because some populations of stink bugs have been showing resistance to certain insecticides.

Pyrethroid insecticides are one of the best ways to control redbanded stink bugs. Loopers, though, are resistant to the chemical, which, in addition to controlling the redbanded stink bugs, also kills beneficial insects that prey on loopers. Acephate also is effective against stink bugs, but it also has the downside of increasing loopers.

“The goal is to develop methods of controlling redbanded stink bugs without increasing soybean looper populations,” he said. “When you remove all beneficial predators, the looper population grows exponentially.”

Loopers don’t overwinter in the U.S. The moths migrate on winds sweeping out of the Caribbean islands and Mexico where high doses of pyrethroids have resulted in resistant populations.

Davis said some populations are resistant to most products available for control.

There are three different chemical options that he will give to growers for stink bug control: neonicotinoids, pyrethroids and organophosphates.

If left unchecked, the redbanded stink bug can cause damage so extensive that farmers may lose an entire field of beans, Davis said.

When asked what the worst insect pest for Louisiana growers is, without hesitation, Davis said the redbanded stink bug is the No. 1 pest of Louisiana soybeans.

“It is the hardest to kill, most destructive, has high populations and is most resistant to the pesticides that we have,” he said.

Three other AgCenter entomologists are also working on a variety of insect issues in corn, grain sorghum and cotton.

Tyler Towles is mainly working with insect pests in cotton, while Fangneng Huang screens different populations of fall armyworms, corn earworm and sugarcane borer to different Bacillus thuringiensis proteins.

AgCenter entomologist James Villegas is continuing ongoing experiments and initiating new investigative aspects to existing soybean insect pest problems and improving chemical control strategies.

“The work that I’m doing involves pest management in corn, soybeans, sorghum and cotton,” he said. “We are looking at ways to manage our insect pests sustainably and try to extend that to our producers.” Johnny Morgan

8/17/2022 7:54:02 PM
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