University of Illinois

No. 2/April 4, 1997

Corn Flea Beetle: Expectations for Injury

A very small insect that causes some anxiety in the seed production business each year is the corn flea beetle. The flea beetle is named appropriately, for its small size (1/16 inch in length) and its impressive leaping ability when bothered. Flea beetles overwinter as adults and are most likely a problem when corn plants are slowed in their development by cool spring conditions. Of utmost concern to the seed industry is the potential for transmission of Stewart's disease or wilt to susceptible inbreds.

Entomologists have long reported that mild winters favor the survival of flea beetles and increase the potential that Stewart's disease may be a problem. In an effort to quantify the effect of winter conditions on beetle survival, it is commonly suggested that if the average monthly temperatures for December, January, and February sum to more than 90, flea beetle survival through the winter may be good.

Bob Scott, Illinois State Water Survey, has provided a map (Figure 1 below) for Illinois that reveals winter temperatures for this 3-month period may have taken their toll on beetle survival for all but the southern onethird of the state. Based upon these temperature totals, beetle survival north of Interstate 70 (approximately) is not expected to be good. This projection is comparable with last year.

We encourage scouting for this insect pest (even in northern Illinois) where sensitive inbreds are being grown. Rescue treatments should be considered if 10% of the corn plants have flea beetle feeding injury and two or three beetles are found per plant. Insecticides labeled as rescue treatments for corn flea beetle control include *Ambush 2E, *Asana XL, *Furadan 4F, Lorsban 4E, *Penncap-M, *Pounce 3.2 EC, Sevin XLR Plus, and *Warrior 1EC (*use restricted to certified applicators only).

Mike Gray, Extension Entomology, (217)333-6652