University of Arkansas Division of Agriculture  |   April 16, 2012 resize text

Many farmers need to budget now for one, and possibly two extra insecticide applications this growing season, as the early spring is expected to provide more time for a crop pests to create an extra generation.

“This is one of the earliest springs we’ve seen in a long time,” said Gus Lorenz, Extension entomologist for the University of Arkansas System Division of Agriculture. “The warmer-than normal-temperatures have allowed insects to get an early start this year. They’re developing at a faster-than-normal rate.”

Insects are expected to have an extra generation this growing season.

Insects that may produce three generations during a growing season “may have a fourth and part of a fifth,” he said. “That may not sound that bad on the surface, but with every new generation, they build up bigger numbers.”

One such pest is the tarnished plant bug, which Lorenz called the No. 1 pest of cotton.

“They’re at huge numbers, much higher than what we usually see at this time of year,” he said. “Based on our observations, we feel there is a much worse situation that’s brewing for the future.”

The higher numbers will mean more spraying.

“Generally, speaking a tarnished bug application will be $8-12 an acre,” Lorenz said. “What this means is increased costs to growers and a more expensive crop.

“It’s nothing we can’t handle. Our growers can manage, but it’s a matter of being able to budget another insect application or two to get a handle on the problem and growers should be prepared for that eventuality,” he said. The downside to extra applications is the loss of beneficial insects that can keep the pests in check.

More sprays early in the season “causes secondary insects like aphids, mites, and even bollworms to become worse,” Lorenz said.

HOST PLANTS
The warm temperatures have accelerated growth of host plants, providing a feast for the early insects. The warmth also accelerated growth of winter wheat, a crop that unfortunately is serving as a host plant for armyworms that arrived in Arkansas a full month earlier than normal, Lorenz said.

Lorenz predicted that “if that wheat field is next to a corn field or a rice field that’s emerging, the armyworms will leave the wheat and go across the turnrow or the highway and go into that seedling crop and eat it right down to the ground, past the growing point. Growers will lose their stand.”

Scouting fields for armyworm activity is of primary importance – and not just in the lower canopy of wheat, but also in the dirt.

“It’s extremely important where rice, or other small grains like corn and milo are growing that you monitor that and be prepared for the armyworms to go across the road,” Lorenz said. “I’ve seen them crossing the road so thick, the road would get slick from people driving and crushing them. They don’t call them armyworms for nothing.”

Armyworms are also masters of the disappearing act.

Lorenz told of one producer with a damaged wheat crop who thought the worms were gone.

“I told him to lift up the dead grass on the ground and tell me what you see. He lifted it up ad said, ‘they’re everywhere!’” Lorenz said.

“Armyworms are like the vampires of the insect world. They don’t like the sunshine,” Lorenz said. The worms will often seek shelter under rocks or clods of dirt. “Fifty or 60 can cram underneath a dirt clod” the size of a half-dollar.

Chuck Wilson, director of the Rice Research and Extension Center in Stuttgart, said pyrethroids were the product of choice and warned producers to spray as late  in the day as possible.
“Pyrethroids break down in sunlight, so late in the day spraying will help maintain activity when the armyworms come out at night.”

Growers should consult the MP-144 “Insecticide Recommendations for Arkansas,” or their county agent.

For more information on crop production and pest control, www.uaex.edu, arkansascrops.com, or contact your local county agent.

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