Prepare to Defend Against Armyworms

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army wormYou may have noticed some invaders in your pastures lately…small resilient soldiers eating, and eating, and eating. Those little intruders are probably armyworms and this is the perfect time of year for you to be thinking about them. Army worms are not very picky and will feed on several crops or pasture grasses around here: millet, grain, sorghum, corn, oats and rye just to name a few!

Fall armyworms can be green, brown or black, and as long as 1.5 inches, but all have a distinctive upside down “Y” design on the head capsule. The adult moths are active at night and have an average life span of 2-3 weeks. The female moths can lay several hundreds of eggs at a time. Late summer and early fall tend to be the periods that we are hit the hardest by these pests. It is best to scout your field when these army worms are active, so early morning or late in the evening is probably your best bet to get an idea of the field infestation.

Like an army, these worms start at the edge of a field (usually) and make their way into the middle. They’ll eat all available plant tissue and move en masse to the next feeding area. Damage varies but the presence of 3-5 medium-large armyworms per square foot justifies some sort of control.

The most common insecticide for army worms is Sevin. It seems to work well in pastures, hay fields, lawns and food plots. As with any insecticide, be sure to check the label and read the directions for pre-harvest grazing and hay cutting restrictions before spraying. The army worms eat Sevin and die 2-3 days, but will stop eating soon after it is applied before dying. It should be applied at least 2-3 hours before rainfall occurs and should dry on the leaves to be truly effective. The common waiting period is 14 days for Sevin before grazing or cutting.

Several other products are labeled for use for army worms in hay crops: spinosad (Tracer), methomyl (Lannate), Bacillus thuringiensis (Agree Wg, Xentari), zeta-permethrin (Mustang Max), and azadirachtin (Neemix 4.5, Azatin XL Plus). Lannate is a restricted use product and can only be applied by a licensed pesticide applicator. It has a 7 day pre-harvest interval for grazing or 3 day waiting period for hay harvest. For other areas, like lawns, Bayer Advanced Complete brand Insect Killer for Soil & Turf or Ortho Bug B Gon Max Insect Killer for Lawns & Gardens may be effective in destroying army worms infestations. Before applying any chemical, be sure to read and follow the product label directions.

Army worms are on the march in Wayne County…don’t let them destroy your fields!!

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. 

Call Stefani Garbacik at the Wayne County Cooperative Extension Office for any pest or forage questions at (919) 731-1525.