Recent rains and cooler temperatures have brought some pest problems for Texas farmers and ranchers. Fall armyworm activity is on the rise in some areas of the state, according to reports from Texas A&M AgriLife Extension Service agents.
Armyworm moths can lay up to 2,000 eggs that hatch in two to three days, according to a 2015 Extension report. There are four to five generations per year.
Farmers should scout their fields each morning for armyworms, because the pests are night feeders that try to avoid daytime temperatures.
The threshold for insecticide spray treating a pasture is three or more armyworms per square foot. Armyworms in those numbers should be treated immediately.
The recommendation is using insecticide labeled for armyworm control in pastures and hayfields.
You don’t need to wait a day if their numbers are at threshold. They are going to do a lot of damage quickly. If you find them in the morning, spray that day.
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 pest got its name because they appear to march across hayfields, consuming the grass in their path.The fall armyworm, Spodoptera frugiperda, is a common pest of Bermuda grass, sorghum, corn, wheat and rye grass and many other crops in north and central Texas. Larvae of fall armyworms are green, brown or black with white to yellowish lines running from head to tail. A distinct white line between the eyes forms an inverted “Y” pattern on the face.
Armyworms are very small (1/8 inch) at first, cause little plant damage and as a result infestation often go unnoticed. Larvae feed for 2-3 weeks and full grown larvae are about 1 to 1 1/2 inches long. Given their immense appetite, great numbers, and marching ability, fall armyworms can damage entire fields or pastures in a few days.
Once the armyworm larva completes feeding, it tunnels into the soil to a depth of about an inch and enters the pupal stage. The armyworm moth emerges from the pupa in about ten days and repeats the life cycle. The fall armyworm moth has a wingspan of about 1 1/2 inches.
Moths are active at night when they feed on nectar and deposit egg masses.
The key to managing fall armyworms is frequent inspection of fields to detect fall armyworm infestations before they have caused economic damage. Once larvae are greater than ¾ inch long, the quantity of foliage they eat increases dramatically. During their final 2-3 days of feeding, armyworms consume 80% of the total foliage consumed during their entire development.
