Soybean research targets old and new pests, evaluates host plant resistance

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LSU AgCenter entomologist Jeff Davis sweeps for insects in a soybean field at the Doyle Chambers Central Research Station.

Soybean farmers are familiar with the damage redbanded stink bugs can cause to their crops. In the first year of a three-year project, the LSU AgCenter has focused on this insect and others, to develop integrated pest management strategies that can help soybean plants resist an onslaught of pests.

The studies are being conducted at five AgCenter research stations: Doyle Chambers Central Research Station in Baton Rouge, H. Rouse Caffey Rice Research Station (South Farm) in Crowley, Dean Lee Research and Extension Center in Alexandria, LSU AgCenter Botanic Gardens in Baton Rouge and the Northeast Research Station in St. Joseph.

One objective is to evaluate 14 commercial varieties to home in on host-plant resistance to insect pests — particularly redbanded stink bugs.

“We’re looking at different varieties in a randomized, complete block design,” said Jeff Davis, AgCenter entomologist and project leader. “How are they going to yield in response to insecticides and how are they responding to the different stink bugs?”

The study is also tracking stink bugs — which taste with their feet (tarsi) and ears (antennae) — to see whether they use pods or leaves to feed and lay eggs. Some farmers believe when the pods are brownish in color, stink bugs like them less, so Davis is trying to understand, from a scientific standpoint, if they have a different sense or taste that guides them to an optimal pod.

The research project is also monitoring the brown marmorated stink bug which first arrived last year in Iberville Parish after making its way from Pennsylvania, having originally arrived there from Asia in 2000. The pest is not only a potential threat to soybean and corn, but also likes to overwinter in houses.

Seed decay can occur when a weather event coincides with the application of harvest aids like desiccants used to dry the beans for harvest. AgCenter pathologists and entomologists are studying fungicides and looking for the best-timed applications to protect the beans.

They also want to find out if stink bugs are increasing the spread of Phomopsis, a type of fungi.

“We’re trying to figure out if stink bugs are transmitting Phomopsis by moving their mouths like a dirty needle,” said Davis. “Can they pick up some of the fungi and transmit it into the seeds directly, which can cause rot?”

Some soybean producers allow grasses and pollinator plants to grow along ditch banks and tree lines as part of a conservation stewardship program. One particular study was initiated because growers wanted to know more about soybean pests and beneficials living in the grassy growth.

“We spray egg whites on those grass sections where we know insects are,” said Davis. “A couple days later, we come into our soybeans, sweep our areas, collect those insects and then we can detect foreign proteins with antibodies in the lab.”

Tests have shown both beneficials and pests have overwintered in the buffer grasses and moved into the soybean plants. Research is ongoing, but measurements indicate the insects have migrated at least 50 meters into the fields.

Monitoring will continue, and if higher populations are detected in certain areas nearer to grass buffer areas, there may be an opportunity to apply site-specific applications using sprayer drones.

An important additional project is an AgCenter entomological collaboration with a University of Missouri plant breeder. Research, funded by the Mid-South Soybean Board, is analyzing new soybean varieties, with potential for greater insect resistance and higher yield potential.

AgCenter entomologists continue to work with agronomists, pathologists and weed scientists testing new and existing soybean insecticides for overall effectiveness against insects and disease. Overall, integrated pest management strategies can reduce insecticide applications and grower costs, while maintaining plant health.

“Soybean is the rotational crop for everybody, and we’re trying to protect it,” said Davis.

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The redbanded stink bug causes more damage to soybeans than any other insect pest.

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Grassy border area between soybean fields at the Doyle Chambers Central Research Station in Baton Rouge. Photos by Randy LaBauve

8/17/2022 7:39:57 PM
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