I have received phone calls of fall armyworms in the area. Fall armyworm numbers are increasing around the state following recent rain events and a drop in temperatures. Armyworms can devastate rangeland and pastures quickly. 

Dr. Vanessa Corriher-Olson, AgriLife Extension forage specialist in Overton, said producers should expect an increase in armyworm numbers following recent rains and cooler temperatures in areas of the state.

Armyworm moths can lay up to 2,000 eggs that hatch in two to three days, according to a 2015 report by AgriLife Extension entomologist Dr. Allen Knutson. There are four to five generations per year.

Corriher-Olson said armyworm caterpillars are picky eaters that prefer high–quality, fertilized forage typically found on fields maintained for hay production. They are a common pest of Bermudagrass, sorghum, corn, wheat, rye grass and many other crops in north and central Texas.

Producers should scout each morning for armyworms, she said. Armyworms are night feeders that try to avoid daytime temperatures.

Armyworms are green, brown or black in color and can be identified by the white inverted Y on their head. They can grow up to 1 inch in length when mature.

The threshold for insecticide spray treating a pasture is three or more armyworms per square foot, Corriher-Olson said. Armyworms in those numbers should be treated immediately. Armyworms in the last two or three days of their larvae stage consume 85 percent of their diet. Applicators should always follow all label instructions on pesticide use and restrictions.

 “They are going to do a lot of damage quickly. If you find them in the morning, spray that day.”

Lonnie Jenschke is and Erath County extension agent. His column appears weekly and online at yourstephenvilletx.com.