Study looks at control of soybean insects

A study by an LSU AgCenter entomologist is questioning whether products sprayed to control redbanded stink bugs also kill natural enemies of soybean loopers.

Controlling loopers has become difficult because they are resistant to pyrethroids, acephate and neonicotinoids, which are sprayed to control redbanded stink bugs, said entomologist Jeff Davis. One product, bifenthrin, provided only 50% control of loopers, he said.

He said research is ongoing to find a product that will control redbanded stink bugs without affecting the looper’s natural enemies.

“So far, we haven’t found any,” he said.

For 2019, the stink bugs were at threshold a month earlier than usual, probably because of the warm winter, he said.

Farmers may want to wait to spray for redbanded stink bugs until the pest reaches the threshold so that spraying also can be done for that pest and loopers in one application, Davis said. It is good policy to budget $15 to $20 per acre for spraying for loopers, he said.

He said treating soybeans for redbanded stink bugs at different growth stages is being studied, focusing on when female stink bugs are at their highest in order to reduce egg lay.

“Last year, we were able to reduce spraying by one application,” he said.

Agronomic practices are also being studied, including the use of border crops, but those approaches could be too costly, Davis said. One approach against stink bugs has been to kill cover crops, especially crimson clover, as early as possible because that plant is the stink bug’s favorite overwintering vegetation.

Research has shown that neonicotinoid seed treatments for soybeans are effective for 21 to 28 days, Davis said, and that could provide protection against early redbanded stink bugs that feed on leaves and stems.

He said two new insecticides that have been effective against redbanded stink bugs could be released as early as 2020.

Two breeding lines grown in Arkansas and Missouri demonstrated good stink bug resistance that eliminated the need for spraying insecticides.

“Hopefully, public breeders will get this germplasm into commercial varieties,” Davis said. Bruce Schultz

11/7/2019 12:26:47 AM
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