Armyworms

Armyworms

Noctuidae family

These are the larvae of several species of night flying moth. Most significant for the vegetable grower is the Beet Armyworm which feeds on a very wide variety of vegetable crops (beans, beets, Brassicas, celery, corn, lettuce, onion, peas, pepper, potato, tomato and more).

The white egg masses have a cottony appearance and contain up to 80 eggs. The newly hatched larvae feed together for a while and spin silky webs around themselves (they feed at night and hide during the day). As they get bigger (eventually to 1 ½”) they disperse and travel from one plant to another (they often migrate into crops from neighboring weeds). If food is scarce large numbers of caterpillars may travel together (in small armies - hence armyworm) and when in sufficient numbers they can skeletonize plants overnight.

The best way to deal with armyworms is to encourage predatory insects such as wasps and beetles. You might also remove egg clusters by hand. If they get out of hand you could spray with BT.

Image: USDA ARS Photo Unit, USDA Agricultural Research Service, Bugwood.org