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Insect pests cost Louisiana soybean producers more than $44 million in lost revenue, according to LSU AgCenter researchers.
A team of AgCenter entomologists continually researches means of controlling these pests to cut spending on insect-related inputs and crop losses.
Each year, the Louisiana Soybean and Grain Research and Promotion Board funds several insect pest management studies.
“We are trying to find solutions that are economical but also science-based,” said LSU AgCenter entomologist James Villegas. “These are practical solutions for our producers to combat their insect pest issues and try to provide different management tools.”
Entomologist Jeff Davis is embarking on a three-year study to evaluate untested commercial insecticides for redbanded stink bug control, and he will work with Daniel Swale, a former AgCenter scientist now at the University of Florida, to design and develop new insecticide options to combat stink bugs.
Stink bugs are highly tolerant of insecticides, and most insecticides that fight them are broad spectrum and affect many insects, Davis said. With the expected ban of the insecticide acephate for agricultural use by the Environmental Protection Agency, additional insecticides labeled for use in soybeans will be needed. Davis, Villegas and entomologist Dawson Kerns are studying other options.
“Reassessing all the insecticides, new labels are going to be had,” Davis said. “They might be removing some, like acephate. One of the first things we’re doing is trying to look for new products that don’t hurt bees because we want to keep all our pollinators around.”
Davis has three products to test from the class of insecticides known as N-arylamides and one product from a group of chemicals called pyrones.
In another study, Villegas is evaluating commercial and experimental insecticides against redbanded stink bugs and soybean loopers. Previous trials found that tank mixes of bifenthrin with acephate or clothianidin provided the best control and longer residual effects, and acephate or bifenthrin alone provided good control depending on the infestation level.
“Doing all these efficacy trials in the field allows us to see what products continuously work against these pests,” Villegas said. “These products vary in modes of action but also, from an economic standpoint, they vary in price.”
Plinazolin — the trade name of Isocycloseram — is expected to be registered soon and has provided excellent control with long residual effects, Villegas’ team found.
“It has a very long residual, so we’re looking at when you can apply that to take advantage of that residual control and maybe you can reduce the total number of applications,” said Kerns, who is also working with the insecticide.
Villegas and his team are assessing the effectiveness of commercially available and experimental insecticidal seed treatments (ISTs) in conventional production systems and double-cropped wheat and soybean production systems.
Neonicotinoid ISTs, such as Cruiser, Gaucho and Poncho, have been accepted in soybean production and have increased yields in the majority of field trials. Producers rely on these seed treatments more often when planting in early spring, Villegas said. Small-field plot trials conducted at the AgCenter Dean Lee and Macon Ridge research stations will collect data on insect infestation levels, seedling vigor and plant stands.
Kerns is also studying commercial and experimental ISTs to enhance soybean insect management strategies for northeastern Louisiana. At the Macon Ridge station, Kerns will test whether producers will see the same value in the seed treatments when planting later in the season.
“The soil temperature is going to be warmer, the seedlings will be more vigorous and a lot of times they can outgrow the damage they receive,” Kerns said.
With AgCenter precision agriculture expert Randy Price, Villegas and his team also will collect data on the effectiveness of sprayer drones in soybean insect pest management. Previous small-plot trials found that sprayer nozzle types had no effect on redbanded stink bug control, and spraying at 2 to 5 gallons per acre provided better control. Also, the optimal spraying heights were found to be between 10 and 20 feet.
“What we’ve seen so far is there’s really not much of a difference whether you’re using a drone or sprayer rig,” Villegas said.
This year they will expand the trials to larger fields that reflect the size commercial producers would use.
Davis will also test whether the harvest aid paraquat increases stink bug feeding. Paraquat mobilizes carbohydrates into simpler sugars, Davis said, and it may attract more insects.
“One of the things we are interested in is when our growers go out and put out paraquat, are they then enhancing these pods to be more attractive to stink bugs?” Davis said.
He will also assess the effects of a sublethal dose of the diamide insecticide Vantacor on redbanded
stink bug reproduction and survival. Research from Brazil has shown that another species of stink bug survived and produced more eggs after a sublethal dose of the insecticide. Davis aims to reproduce the research on redbanded stink bugs in greenhouse and field settings.
Redbanded stink bug adult. Photo by James Villegas
