Most recently reviewed by: Ed Bynum (2018)
Common Name(s): Fall Armyworm
Pest LocationRow Crop
Adult moths have a wingspan of approximately 1.5 inches. Females have front wings that are dark grey. Males have wings that have light and dark areas throughout and a whitish area near the tip.
Eggs are laid in groups of 100 to 200 and are covered by grey scales from the female moth’s body. The scales often impart a “fuzzy” appearance to the egg mass. Eggs are pearly green in color when newly laid and darken to a brown color in about 12 hours. Just prior to larval hatch, which occurs in 3 – 7 days, the eggs become blackish colored.
Small larvae range in color from a light cream when newly hatched to greenish after feeding, while medium-sized larvae range from light green to olive-green or brown. As with most larvae, identification in the first growth stage is difficult. To distinguish young fall armyworm larvae from those of the corn earworm and southwestern corn borer, look for a small black spot on the side of the first abdominal segment, just behind the last pair of true legs on the thorax. Fall armyworm has such a spot and the other two species do not.
Color characters are not very reliable for fall armyworm larval identification. Older larvae vary in color from light tan or green to blackish, and can change color as they mature. They have three fairly narrow stripes down the body as viewed from above; one down the centerline and two widely separated by darker areas. These may be variously colored, from whitish to yellow-white to reddish. There is a wider dark stripe down the side of the body and a wavy yellow-red blotched stripe just below this.
The best field identification characters do not involve color. Larvae have four pairs of abdominal prolegs and a pair of anal prolegs at the tip of the abdomen. They also have four dark spots arranged in a rectangle on the top of the eighth abdominal segment near the end of the abdomen.
Older fall armyworm can be distinguished from true armyworm, corn earworm, and the corn borer species by the presence of a white inverted “Y” mark on the front of the dark reddish-brown, mottled, head capsule. This character may be absent on younger larvae.
Origin and Distribution
Fall armyworm is native to the Western Hemisphere and overwinters in areas of mild climate.
Fall armyworm adults migrate north from overwintering sites in south Texas and northern Mexico and become established in corn and other crops in the spring. Fall armyworm does not overwinter in the northern part of Texas and does not undergo winter diapause. This species has a very broad host plant range that includes wheat, alfalfa, sorghum, corn, and other crop and non-crop plants.
Fall armyworm larvae feed 2 to 3 weeks. Mature larvae burrow an inch or two in the soil to pupate. Pupation lasts for about 2 weeks. Pupae are smooth and reddish brown to dark brown in color and look much like the pupae of other lepidopterous pests of corn. Adults then emerge to mate and females can lay up to 1,100 eggs. Adults live about two weeks. There are several generations each year, and migratory moths may continue to arrive throughout the season.
There are two host strains of fall armyworm, one of which feeds predominately on corn, sorghum and cotton (known as the corn strain), and the other, the rice strain, feeds on rice, Bermudagrass and Johnsongrass.
The fall armyworm and true armyworm get their names from the behavioral trait that causes larvae to move from one field to another when they have consumed all available food. In essence, they are said to move like an army.
ManagementIf you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.
Home garden control options include:
- Spinosad (Rate varies by brand name)
- Permethrin (small larvae only)
- Synthetic pyrethroids (small larvae only)
- Bacillus thuringiensis (Bt. subspecies Aizawai)
- Managing Insect and Mite Pests of Texas Corn
- Managing Cotton Insects in Texas
- Managing Insect and Mite Pests of Texas Sorghum
- Managing Soybean Insects in Texas