Fall armyworm migrates from the south flying hundreds of miles northward. This pest has been found the last two weeks feeding in grass pastures, summer grass annuals, alfalfa and soybeans in south Missouri so we should scout our local crops.
Damage from larvae can be extremely damaging. Damage in pastures often occurs quickly giving the appearance of damage overnight. Larvae are active in mornings and evenings. Tall fescue and orchardgrass are favorite host plants. Be sure to check fields carefully as they may be on side of the field and not uniformly across.
The economic threshold is to treat if three or more larvae are present per square foot. Use insecticides labeled for this pest. Avoid using pyrethroids as fall armyworm in Arkansas had developed resistance to this class of insecticides. Also use 20 gallons or more of water per acre as a carrier.
Color is not a good identifier as they change color. Young larvae may be dirty white and may change to light tan or pinkish gray as the larvae mature.
For more information, contact Wayne Flanary, field specialist in agronomy, University of Missouri Extension at 816.279.1691.
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