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Heat aids soy-marauding worms

High temperatures are giving an edge to bollworms attacking Arkansas’ soybean crop, University of Arkansas Division of Agriculture personnel said Tuesday.

The flight of bollworms is so bad, “we have the potential with the high numbers we are experiencing to see very high yield loss,” said Gus Lorenz, extension entomologist with the Division of Agriculture. “This is one of the worst bollworm infestations we’ve had in soybeans in many, many years.”

The worm densities are so high in some cases, “if you get 90 percent control, you’re still at treatment level,” he said.

The triple-digit heat and cloudless days are causing fast evaporation and convection, preventing insecticides from reaching down into the canopy where the bollworms are sheltering, laying eggs and chowing down at the soybean buffet.

“We are seeing what are called ‘control failures,’ which is probably caused in part by evaporation of the product before it gets to the right place,” Don Plunkett, Jefferson County extension staff chair for the U of A Division of Agriculture, said Tuesday.

“Water is the cheapest insecticide,” Plunkett said. “It’s just wasted money if the product is just floating around in the air and dissipating.”

“It’s all about application volume,” Lorenz said. “History tells us the more volume you have, the better off you are.

“If you’re making an aerial application of 2 gallons per acre, if it’s being applied in the middle of the day, that’s when the heat is really going to vaporize it before it gets to the canopy,” he said. “More volume is going to improve penetration.”

Lorenz is recommending a minimum of 5 gallons of water per acre for aerial applications and 10 gallons per acre for ground applications.

“We’re also recommending they use crop oil at 1 percent with the application to help the insecticide penetrate down in the canopy,” he said.

For producers still recovering from last year’s wet harvest and paying higher prices for diesel to run water pumps, every pesticide application has to count.

“The worst application is the one that doesn’t work,” Lorenz said. “It lends itself to people getting very frustrated. The heat already has people short-tempered.”

Meanwhile, Lorenz and his crew are trying to beat the heat by starting their day at 6 a.m. and winding up at 2 p.m. Unfortunately, by 12:30 p.m. Tuesday, the official National Weather Service reading at Little Rock Adams Field was 104. The weather service said Wednesday a record high of 107 degrees was set at Little Rock just after 2 p.m. on Tuesday.

“We’re doing what we can to hold up,” he said.

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

TAGS: Soybean
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