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Welcome rains bring unwelcome visitor: Fall armyworms

Friday, July 27, 2012

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Where rain has returned in sufficient amount to make pastures green again, so have fall armyworms, an annual scourge ready to mow those luscious new blades of grass, Kelly Loftin, extension entomologist for the University of Arkansas System Division of Agriculture, reported.

Parts of Cleveland County have received 3 to 11 inches of rain in the last two weeks, reviving parched pastures and making them a target for the fall armyworms.

"I looked at two farms and both had armyworms, and neither of the producers was aware of it," Les Walz, Cleveland County Extension staff chair for the University of Arkansas System Division of Agriculture, said. "It's pretty bad. We're seeing eight to 15 worms per square foot."

Loftin said the threshold to take action to control the moth larvae is three worms per square foot.

Moths that produce fall armyworms seek out the lush grass to lay their eggs. The eggs, attached to the underside of grass blades, are very hard to see.

However, "the big thing is to look for the worms before they get too big to control," he said. "Once they get up to 1.5 inches, they've done a lot of damage." Eighty percent of what the worms eat is consumed during their last two growth stages.

Other than seeing the worms themselves, Loftin said another method of early detection of an infestation is "a slight frosted appearance in the field. This is because the tiny larvae are feeding on the underside of the blades, and at this size are only able to eat through the lower epidermis. "This results in a windowpane on the grass blade, giving the field a frosted appearance," he said.

Ideally, producers should catch the worms before they get bigger than a half-inch long.

"At .75 of an inch, you have to use high rates of pesticide to control them," Loftin said.

Both Walz and Loftin can't stress scouting enough -- especially during a time when 83 percent of the state's drought-blasted pastures and range are rated poor or very poor.

For more information on armyworms call your local county Extension office.



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