Entomologists battle pests in soybeans

LSU AgCenter entomologists are focusing on several fronts to protect soybean plants from insect pests.

Jeff Davis has multiple projects that approach control of stink bugs and lepidopteron defoliators in different ways.

One ongoing project is testing new and improved insecticides and their applications. Davis said lately that means testing more natural products that use biological control methods and can go through testing by the Environmental Protection Agency more quickly than synthetic insecticides.

“We do efficacy trials. We are trying to get ahead of the game so when they do make it to the growers, we have some good information,” Davis said.

Davis also is keeping a close eye on the brown marmorated stink bug. This insect first showed up in Louisiana in 2021, and it hasn’t moved much from Iberville Parish where it was first detected.

Unlike the redbanded stink bug, which feeds primarily on soybeans, the brown marmorated stink bug will infest soybeans, corn, cotton, fruits and vegetables and can be found in people’s homes and in gardens.

“Anything you may have in your garden will also be building those populations,” Davis said. “We’re putting out traps around the state to see if it moves.”

Methods used to control the redbanded stink bugs will also control the brown marmorated.

Soybean growers asked Davis to investigate whether stink bugs feeding on soybean pods is leading to seed decay seen in some fields. Davis said over the past five years whenever hurricane or heavy rain occurs near harvest, growers see a lot of seed decay.

“Any feeding can cause a wound on the pod and that creates an opening for disease to come in, just like if you have an opening in a screen on your house you might have mosquitoes and termites come in,” he said. “So, we are looking at does stink bug feeding, probing on those pods, cause more seed decay and can we prevent it.”

Davis is working to determine if timely insecticide applications or insecticides with a fungicide can decrease seed decay. He also is seeing if applying harvest aids near a rain fall leads to seed decay.

The fourth area of focus for Davis is to determine how areas in conservation stewardship programs adjoining cropland may harbor pests.

“Growers came to me and asked questions about if they participate in these conservation stewardship programs does that affect insect populations,” Davis said.

Davis is using a mark and capture technique to detect insect movement from the conservation areas into fields. Davis sprayed the conservation areas near fields with egg whites, which act as a natural biomarker on insects. He then came back and did insects sweeps at different lengths starting with the conservation areas and moving into the fields. Analyzing the captured insects, he could see the amount of movement.

“I’m not saying we aren’t seeing any movement, but it’s not as much as I thought, and they are not providing that much of a detriment to our growers,” he said.

AgCenter field crops entomologist James Villegas is also helping growers battle insect pests in their fields.

Farmers and insect scouts started seeing redbanded stink bugs early this year in their fields. Villegas said they had hoped the late cold snap would have decreased the population, but it seemed to have little effect.

He is conducting research on insecticidal seed treatments for early season soybean pests. He said results on those studies haven’t been as consistent as he would like, but in good conditions, it appears that seed treatments are not needed.

“If we plant right after wheat or in a weedy field, then we get a lot more benefit from these seed treatments,” Villegas said.

Villegas also is collaborating with researchers at other universities in the Midsouth to look at different combinations of insecticides and whether they are still working effectively against redbanded stink bugs.

“The other states really rely a lot on the data coming from the Midsouth group, especially the data coming from Louisiana because normally we have higher infestations than, for example, Mississippi or Arkansas,” he said.

New this year is Villegas’ work with sprayer drones. He is working with AgCenter engineer Randy Price to build drones that can carry insecticides and spray small research plots.

“I want to see what the role of sprayer drones could be, particularly in integrated pest management,” he said.

Villegas or research assistants often walk research plots with backpack sprayers. Sprayer drones would allow insecticides to be applied even when fields are too wet to traverse. He is hoping to create standards for sprayer drones and help answer questions that are starting to arise as consulting companies start to offer sprayer drone services.

Insect management strategies applied to corn and grain sorghum

The cold spring slowed the emergence of corn leading to a heavy population of soil-borne insects according to LSU AgCenter field crops entomologist James Villegas.

Part of Villegas’ research focus is controlling pests in corn and grain sorghum. He said wireworm has his attention this year.

“I've talked to consultants up north, and some producers ditched their fields, 200-acre fields of corn because of wireworm problems and just planted beans,” Villegas said.

Wireworms can live in the soil for a long time. He said certain species can stay as larvae for up to three or four years, making them hard to control and predict.

Low acreage of grain sorghum has made it difficult to conduct research on that crop, but Villegas is looking at the sugarcane aphid and head worm complex and how those pests are affecting sorghum.

“We only have two foliar products available on the market that are effective for sugarcane aphid control and that would be Transform and Sivanto,” he said. “In terms of head worms, Vantacor and diamide products are still pretty good towards it.”

9/14/2023 3:16:52 PM
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