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Entomology: Insects Associated With Vegetable Crops in Georgia

Other Armyworms

(Order: Lepidoptera, Family: Noctuidae,   PDF file
Southern armyworm (Spodoptera eridania (Cramer))
Yellowstriped armyworm (Spodoptera ornithogalli (Guenée))

Description:

Yellowstriped armyworm.

Adult: Southern armyworm moths are medium sized with a wingspan of 33-38 mm, while yellowstriped armyworm moths have a wingspan of 34-41 mm. The forewings of both are grayish brown with light and dark colored markings. The hind wings are a more uniform white or with a narrow brown margin.

Immature stages: Eggs are laid in clusters of 200-500, greenish to white and are covered with a layer of whitish scales that give the egg mass a fuzzy or cottony appearance. Southern armyworm eggs have ribs which radiate out from the center. Larvae are pale green to yellow during the first two instars. Larger larvae of both species are similar in appearance. Large southern armyworms are tan brown to dark green with a reddish brown head. They have white lines on the back and additional stripes on the side interrupted by a dark spot on the first abdominal segment. The yellowstriped armyworm has two yellow colored bands down each side of the back with a series of strong black triangular markings down either side. The head capsule tends to be darker than the southern armyworm

Biology:

Photo: Southern armyworm feeding on surface of tomato fruit
Southern armyworm feeding on surface of tomato fruit.

Life cycle: Egg clusters are usually deposited on the underside of leaves. Females normally deposit 200-500 eggs during their lifetime. Eggs hatch in 3-6 days during warm weather. Early instar larvae are gregarious, feeding as a group and skeletonizing leaves. Larvae are primarily, if not entirely, foliage feeders but can attack the fruit, feeding mainly on the surface. Normally, larvae develop through 6 instars in 14-20 days. Larvae reach a maximum size of about 35 mm. Pupation occurs in the soil and the pupal stage generally lasts 11-18 days. Total generation time is about one month.

Seasonal distribution: Armyworms generally do not overwinter in Georgia but can migrate readily from Florida. There is an estimated four generations per year in Florida. While the potential for significant infestations is more likely in the fall, this pest can be a problem in spring production season as well.

Photo: Armyworm damage to young pepper plant
Armyworm damage to young pepper plant.

Damage to Crop: The first two instar larvae are gregarious and feed in groups on foliage. The clumped skeletonizing of foliage is known as an armyworm 'hit' in many crops. Third and later instar larvae disperse and may continue feeding on foliage but can also scar the surface of the fruit. Yellowstriped armyworm rarely reaches levels that require control in Georgia.

Management: Armyworm moths can be monitored with pheromone traps, but adult abundance does not always correlate with subsequent larval problems. Scouting for armyworms generally involves inspection of foliage for egg masses, larvae, and 'hits.' Egg masses can be difficult to locate because of their clumped nature. In fruiting vegetables, insecticide applications based on the detection of 'hits' generally provides ample protection, as the early instars do not attack fruit and 'hits' can be detected prior to fruit damage. Southern armyworm has traditionally been easily controlled with insecticides. The armyworms included in this group are usually controlled with applications targeted at more important worm pests such as tomato fruitworm or beet armyworm.

Return to Vegetable Crops

Prepared by Dr. Alton “Stormy” Sparks, Jr. and Dr. David G. Riley - University of Georgia

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University of Georgia (UGA) College of Agricultural and Environmental Sciences (CAES)