The corn flea beetle is a small, shiny black beetle that chews long, parallel lesions in the leaves of seedling corn. Feeding damage first appears as thin, silvery or white streaks. Heavily injured leaves turn brown, wilt and die.
Damage is considered severe when one or more leaves of seedling corn are killed.
Some heavily damaged fields have a frosted appearance when viewed from field edges. These flea beetles overwintered as adults and should mate, lay eggs and die in the next week to 10 days. Transmission of Stewart's disease to corn plants can be limited by controlling the corn flea beetle with an insecticide because the bacterium is transmitted to corn through leaf feeding by infected beetles. That decision should be made based on the actual situation in a given field. For seed corn with inbred lines that are susceptible to Stewart's disease, consider treating when 10 percent of the plants exhibit severe feeding injury and two or more beetles are found per plant.