Helicoverpa zea
From Bugwoodwiki
|
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.
Contents |
Description
Corn earworm may also be called bollworm or tomato fruitworm.
Adult
Wingspan of 1 to 1 1/2 inches. Usually light, yellowish-olive in color, with a dark spot near the center.
Larvae
Variable colors; five pairs of prolegs. Newly hatched larvae are less than 1/8 inch long, yellowish white with a dark head. Second instars are yellow-green, often with darker longitudinal stripes and red-brown to brown head. Later instars may be green-yellow, reddish, or brown with pale, longitudinal stripes, raised black spots, and brown heads. Mature larvae reach up to 1 3/4 inches.
Hosts
Corn is preferred host. Will infest more than 100 different hosts, including many other agronomic crops. Wild hosts include toadflax and vetch.
Damage
Prefer fruiting bodies of host; will also attack foliage, especially tender growth. First generation larvae often feed in corn whorl, causing ragged holes that appear when leaves unfurl. Excreta will collect in whorl. Larvae move to flower buds and fruiting bodies as they appear. Larvae are cannibalistic; typically one larvae per feeding site.
Life Cycle
Overwinter as pupae in about two inches of soil. Adults emerge in April-May, mate, and lay eggs. Most eggs laid on corn leaves if available; most eggs laid on silks as they appear. Eggs laid on other hosts as corn silks dry down. Up to 3,000 eggs are deposited individually by each female.
Eggs hatch in 2-5 days; larvae feed for 2-4 weeks and pupate in the soil for 2-4 weeks. Entire life cycle, 4-8 weeks. Several generations per year.
Control
Plant resistant varieties when available. Cultivate crops after harvest to destroy pupae. Watch for population movement to other hosts as corn dries down. Regular applications of insecticides may be necessary to protect vulnerable crops. When possible, use pesticides that will have the least effect on beneficial populations; this pest is attacked by many natural enemies. Organophosphates, carbamates, pyrethroids, and Bacillus thuringiensis are commonly applied.
 Photo by Johnny N. Dell, , Bugwood.org Adult |  Photo by R.L. Croissant, , Bugwood.org Larva on corn. |  Photo by Art Cushman, USDA; Property of the Smithsonian Institution, Department of Entomology, Bugwood.org Life cycle diagram. |
