UACES Facebook Armyworms in Arkansas | Scouting and treating for true and fall armyworms

Armyworms in Arkansas

Arkansas is home to two kinds of armyworms – true armyworms and fall armyworms. During their last two stages of growth, they eat tremendous amounts of grass so scouting pastures for armyworms is essential.

Download Managing Armyworms in Pastures & Hayfields

What is the difference between true armyworms and fall armyworms?

close up of a true armyworm on a fingertip- brown net-like pattern on head
TRUE ARMYWORM - A key characteristic of true armyworm larvae is a brown net-like pattern on the head.

True armyworms are usually a springtime pest, especially in northern Arkansas on cool season grasses. But they can also be a problem in southern Arkansas. Fall armyworms are more common in southern Arkansas, and they appear in midsummer especially in bermudagrass pastures.

Fall armyworms have dark stripes and a light-colored marking that looks like an inverted Y on their heads. Fall armyworms are sensitive to cold and overwinter in southern Florida, southern Texas and in Central and South America. Fall armyworms typically don’t debut until July, but with a relatively warm winter and spring damage could be seen sooner.

True Armyworms

True armyworms appear in spring and look similar to fall armyworms, and both can be very destructive. True armyworms are green with brown or black paired spots along their backs. 

Download true armyworm fact sheet

When and how should I look/scout for true armyworms?

Arkansas producers are encouraged to diligently scout their pastures and hayfields for armyworms. Examine at least 10 one sq. ft. samples at random across the field. Female armyworm moths prefer to lay eggs in areas of abundant growth, be sure to include a few of these areas in your 10 samples.  

What kind of damage do true armyworms do?

The true armyworm (armyworm) can be a serious pest of pastures, hayfields and seed production fields reducing both forage availability, hay yields and seed production. Damage can appear almost overnight and infestations can be easily overlooked when the caterpillars are small and eating very little. Armyworms are a greater problem during spring, after which time, natural controls usually keep the population below threshold level. Armyworms often feed at night and remain hidden in ground litter by day. 

close up of fall armyworm larvae head with "Inverted Y" arrow pointing to the shape on the head
FALL ARMYWORM  Key characteristics are dark stripes and a light-colored marking that looks like an inverted Y on their heads.

Fall Armyworms

Fall armyworms feed on variety of forage crops but often prefer lush green well-fertilized bermudagrass which is often found in residential areas and yards.

Download fall armyworm fact sheet

When and how should I look/scout for fall armyworms?

Arkansas producers are encouraged to diligently scout their pastures and hayfields for FAWs. Examine at least 10 one sq. ft. samples at random across the field. Female fall armyworm moths prefer to lay eggs in areas of abundant growth, be sure to include a few of these areas in your 10 samples.

 What kind of damage do fall armyworms do?

The fall armyworm (FAW) is one of the most devastating pests of pastures and hayfields, reducing both forage availability and hay yields. Damage can appear almost overnight and infestations can be easily overlooked when the caterpillars are small and eating very little. Beginning as early as late June or July significant fall armyworm populations can occur in Arkansas.