Extension agronomist suggests to scout small grains, pastures for true armyworm

By Wayne Flanary, Extension field specialist in agronomy

True armyworm is a pest that can occasionally occur in area winter wheat fields. This is the first report I have received regarding true armyworm. So, watch fields carefully.

Small larvae feed on lower parts of grass plants and are hard to find. As the larvae mature, they move upward. Economic damage occurs when the flag leaf of winter wheat is fed on. Also, not often, true armyworm can clip seed winter wheat seed-heads.

True armyworms migrate into the state from south. I have caught several moths in the MU insect pest monitoring network at the Forbes location which indicates at least the pest is in the area and/or may have moved through the area.

Scout for this pest in three linear feet of row in five or more areas. Check plants for feeding on the leaf edges when larvae are small and for feeding on flag leaf or head cutting. The threshold is when four or more half grown worms are found per square foot. This may need to be adjusted based on current grain prices.

Several insecticides are labeled for control in winter wheat. The effectiveness of insecticides may be reduced during cool weather. Also, parasitized larva should be considered when making control decisions.

For more information, contact Flanary at 816.279.1691.