Rotate ways to control insects in soybeans, field corn and grain sorghum

Frances Gould, Schultz, Bruce  |  10/13/2016 6:14:15 PM

Jeff Davis, LSU AgCenter entomologist, checks a trap for soybean loopers at the Iberia Research Station near Jeanerette. Photo by Bruce Schultz


Jeff Davis, LSU AgCenter entomologist, said farmers should consider rotating other insecticides with acephate, the main product recommended for redbanded stink bugs, because of increasing acephate resistance.

He said some areas are showing acephate has lost its effectiveness completely against the pest.

Davis said he is advising farmers to avoid using acephate for several years to see if stink bugs lose resistance.

Other chemicals are available and include neonicotinoid and pyrethroid insecticides, such as Endigo ZC, Leverage 360 and Karate, he said.

But those chemicals kill beneficial insects and could cause a flare-up of soybean loopers, he said. Soybean loopers can be treated with other chemicals, such as Prevathon or Intrepid Edge, but the insect is developing resistance to those products, Davis said.

He said genetic studies will be conducted on loopers to determine if the pests originated in areas of the Caribbean where resistance to specific chemicals has developed.

Commercialization of any new insecticides has slowed in recent years, he said. But advances are being made toward improved soybean varietal resistance. “Resistance is the long-term answer,” Davis said.

Julien Beuzelin, LSU AgCenter entomologist, said he is continuing his work on the relationship between soybean, weeds and insects.

“What we’ve seen is fairly straightforward,” he said, adding that redbanded stink bug pressure is higher when weeds are managed well.

“Weeds consistently cause yield losses, while losses from insects are more variable.”

Beuzelin said 2015 was the last year of his three-year threecornered alfalfa hopper study. Data have shown that the threat from this insect was overstated, he said. “We don’t have to be as aggressive as we were in the past.”

David Kerns, LSU AgCenter entomologist, is working on insect pests of soybeans, corn and grain sorghum. He is conducting a study to determine if Prevathon, which is used in soybeans for caterpillar control, has activity on Dectes stem-boring beetles that mine into soybean stems and petioles. The project also includes an evaluation of the pest’s economic impact.

He is looking at older insecticides to see if they have any application for controlling redbanded stink bugs. “One of the problems is there are some severe plant-back restrictions on neonicotinoids in soybeans when followed by sugarcane.”

He also is continuing a studying of the threecornered alfalfa hopper to measure the amount of injury caused by the insect.

“There is a great deal of confusing information regarding the impact threecornered alfalfa hoppers may have on soybean yield. Last year, we were able to measure a yield impact, but it was on beans subjected to a great deal of drought stress,” he said.

In field corn, Kerns is looking at seed treatments to control soil-dwelling insects and seedling pests such as cutworms and sugarcane beetles. He said new and old insecticides are included in that study. Other corn studies involve evaluating Bt traits for efficacy toward ear-feeding caterpillars.

In grain sorghum, Kerns is evaluating materials for managing sugarcane aphids. In addition, work continues on establishing an action threshold for treatment based on a crop’s growth stage and plant resistance to the sugarcane aphid.

Research on the aphid includes a study of the overwintering biology and the host range.

Work continues to identify sugarcane-aphid-resistant hybrids, Kerns said. “That’s going to be the answer to economically managing sugarcane aphids in the long run.”

Bruce Schultz

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