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Bollworms running 10 times recommended treatment levels

Bollworms running at 10X action threshold. High heat, larvae numbers undercutting controls.

Bollworms are the latest challenge for Arkansas soybean growers, with numbers running 10 times higher than recommended levels of action.

“We observed a field that was running 91 larvae per 25 sweeps,” said Gus Lorenz, Extension entomologist for the University of Arkansas Division of Agriculture. “The threshold is nine per 25 sweeps.”

Sweeping is a method of sampling for insect populations in crops using a large fine-meshed net. When a certain density of insects is discovered – the threshold -- certain actions for control are recommended.

“Based on our trap counts, we expect numbers to remain high through at least the middle of August. Treatment levels have been observed from the Bootheel of Missouri to the Louisiana line and up into the Arkansas River Valley.”

Lorenz said fields a highest risk are those with soybean plants that are blooming or about to bloom, are beginning to set pods and have not achieved canopy closure.

In some cases, the numbers of insects is overwhelming common control methods. The high heat has been an ally for the invaders, causing some insecticides to evaporate before hitting their targets. Lorenz recommends using five gallons per acre if being applied by air and 10 gallons per acre if the treatment is ground-applied.

The forecast is not favoring producers, with highs each day this week expected to exceed 100 degrees.

See more of Lorenz’s recommendations here.

For more information on crop production, visit, or contact your county Extension office.

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