Friday, September 21, 2012

Fall Armyworms Threaten Forages in the Ozarks Says MU Extension Specialist

Fall armyworms have found their way into forage crops in southwest Missouri according to Tim Schnakenberg, an agronomy specialist with University of Missouri Extension.

“Recent reports of feeding of fall army worms have been made on alfalfa and cereal crops used for forages (rye, wheat) in the southern tier of Missouri counties,” said Schnakenberg.

The larvae of army worms will “march” across fields consuming every green blade of grass or leaf that it can, totally inundating forages and some row crops. More than 60 plants have been reported as hosts of the fall armyworm, including rye, wheat, orchardgrass, corn, grain sorghum, alfalfa and vegetable crops.

“Southwest Missouri farmers should be scouting their fields for any fall armyworm activity, especially newly planted fields,” said Schnakenberg. “Hot, dry weather tends to favor fall armyworm activity, so we are hopeful that a transition to cooler weather will slow their development.”

According to Schnakenberg, the activity of army worms often is missed because their damage from the windshield of a car can be mistaken for other issues. A closer look reveals ragged leaves and major defoliation.

“Scouting is best done in the early morning hours before the heat drives them into sheltered areas,” said Schnakenberg.

If army worms are active in a pasture or hayfield, the best option is to graze or harvest as soon as possible to minimize the damage.

“The decision this time of year to spray is more difficult, since we are late in the growing season. It depends on the value of the crop and the stage of crop growth,” said Schnakenberg.

The economic threshold that is followed is to spray if there are four or more non-parasitized half grown or larger worms per square foot. The threshold is lower if the pest is attacking newly planted forages.

For more information on control options for fall armyworm contact one of the following MU Extension agronomy specialists located in southwest Missouri: Tim Schnakenberg in Stone County (417-357-6812), Brie Menjoulet in Hickory County (417-745-6767) or Wyatt Miller in Barton County (417-682-3579).


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