Farm Talk

Crops

September 1, 2010

Armyworms finding forage crops in Missouri

Parson, Kansas — Fall armyworms have found their way into forage crops and some row crop fields in southwest Missouri according to Tim Schnakenberg, an agronomy specialist with University of Missouri Extension.

“Reports of major feeding of army worms on bermudagrass and alfalfa have come from Christian County,” 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 row crops.  More than 60 plants have been reported as hosts of the fall armyworm, including corn, grain sorghum, alfalfa, grass pastures and hayfields and vegetable crops.

“Southwest Missouri farmers should be scouting their fields for any fall armyworm activity,” said Schnakenberg. “Hot, dry weather tends to favor fall armyworm activity.”

According to Schnakenberg, the activity of army worms often is missed because their damage from the windshield of a car can be mistaken for browning that is caused by drought. 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.

For more information on control options for fall armyworm contact one of 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 Jay Chism in Barton County 417-682-3579.

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