Spodoptera exigua

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Arthropoda
Subphylum	Hexapoda
Class	Insecta
Subclass	Pterygota
Infraclass	Neoptera
Superorder	Holometabola
Order	Lepidoptera
Superfamily	Noctuoidea
Family	Noctuidae
Subfamily	Noctuinae
Tribe	Prodeniini
Genus	Spodoptera

Scientific Name

Spodoptera exigua

Common Name

beet armyworm

Roberts, P. M. and G. K. Douce, Coordinators. 1999. Weevils and Borers. A County Agent's Guide to Insects Important to Agriculture in Georgia. University of Georgia, Col. Ag. Env. Sci., Cooperative Extension Service, Tifton, GA, USA. Winter School Top Fifty Agricultural Insect Pests and Their Damage Sessions, Rock Eagle 4-H Ctr., Jan. 20, 1999.

Description

Adult wingspan of the beet armyworm is about 1 inch. Forewings are mottled gray or brown with a pale spot near the center. Hind wings are white with dark veins and a fringe-like border.

Larva

Green or black, with a dark head, five pairs of prolegs, and sometimes three lightly colored stripes running the length of the body. On the second segment behind the head, there is a small black spot on each side of the body. This spot usually becomes visible to the field observer when the caterpillar reaches about 1/3 of an inch. The spot may be difficult to see on a dark caterpillar. Squeezing the caterpillar from the rear may make the spot more apparent. Larvae range from less than 1/10 of an inch when newly emerged to about 1 inch when fully grown.

Hosts

Weeds, asparagus, cotton, corn, soybean, tobacco, alfalfa, table and sugar beets, pepper, tomato, potato, onion, pea, sunflower and citrus. Plantain, lambsquarters and redroot pigweed are important wild hosts.

Damage

Gregarious early instars typically damage young terminal growth. Profuse silk webbing may give infested plants a shiny appearance. Later instars feed on foliage and other plant parts; no webbing is produced.

Life Cycle

Beet armyworms are found year-round in Florida and California. Pupae may overwinter in Georgia in the upper 2.5 inches of soil. Georgia crops often infested by moths migrating from warmer areas. Females lay clusters of about 80 eggs in the spring, up to 600 eggs in 3 to 7 days. Eggs hatch in 2-3 days, spin loose webs, and feed gregariously for several days. Then they spread to different parts of the plant and feed for 1-3 weeks before pupating in cocoons of soil, leaf particles and other debris. Moths emerge in about 1 week and live for 4-10 days. The entire life cycle is about 4-5 weeks. There are several generations per year in Georgia.

Control

The beet armyworm has few effective parasites, diseases, or predators to lower its population. Beet armyworm populations are difficult to control. Organophosphates or carbamates are often recommended.

Larva