Timing critical with fall armyworms

Ravenous fall armyworms are leaving browned strips in their wake as they eat through pastures statewide, personnel for the University of Arkansas Division of Agriculture say.

“What should be lush and green is brown and ugly,” said Don Plunkett, Jefferson County Extension staff chair. “Fall armyworms are marching through bermuda hay meadows along the Arkansas River in our county.”

Danny Murdock, a producer in Sherrill, said armyworms had munched their way across areas of recently cut bermuda hay — hay that’s been fertilized in hopes of getting one more cutting before the first frost.

“Other hay producers should be on the watch for signs of armyworm feeding in their pastures or hay crops,” Plunkett said. “The signs of feeding are usually easy to spot if the producer has ever had to watch for signs. Leaf scarring is evident in the bermuda, broadleaf signal grass and crabgrass in fields. Less damage is evident in bahiagrass pastures or hay than in the bermuda crops.”

The full-grown larvae vary in color from light tan or green to nearly black, with stripes down the side. The head is dark with a prominent, light cream-colored, inverted “Y” on the front of the head.

“Fall armyworms do not overwinter in Arkansas,” said Mark Keaton, Baxter County Extension staff chair. “Adult moths catch wind currents and gradually move into the state from the south and lay eggs.”

Fall armyworm damage can appear almost overnight. Infestations can be easily overlooked, when caterpillars are small and eating very little. Once caterpillars grow large and consume more grass, damage becomes apparent.

Fall armyworm infestations can be expected through September.

Keaton advised against treating with worms when they’re tiny. “Several natural enemies such as parasites, predators and pathogens occur and possibly can eliminate or reduce populations quickly. But do not wait until they become too large.”

Pyrethroids are effective against fall armyworms and complete information is available through the U of A Division of Agriculture publication MP 144 2009 Insecticide Recommendations for Arkansas. This publication is also available online at www.uaex.edu/Other_Areas/publications/HTML/MP-144.asp.

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