Purdue University
Cooperative Extension Service
Department of Entomology
Publication E-17 May 1970
CORN BORER CONTROL
Corn borer populations vary greatly from year to year and from field to field. Damage may be caused by either the first or second generation of the borer, but seldom by both in the same planting. Early-planted corn is susceptible to first-brood attack, and late-planted corn to second-brood attack. The first brood burrows in the stalks, whereas the second brood also attacks the ears and ear shanks.
PREVENTING BORER DAMAGE
Cultural Practices
Corn borer damage can be reduced by avoiding, if possible, extremely early or late planting. Farmers who are prepared to apply an insecticide for borer control, if need be, should plant as early as possible. This practice may increase first-brood attack which is easy to control with insecticides, but it will reduce second-brood attack, which is difficult to control.
Plant hybrids that are adapted to your locality. Most adapted hybrids will stand up, hold their ears and produce high yields in spite of corn borer attack.
Destroying corn stalks and other refuse in which the borers overwinter might help, but there is no evidence that such "clean-up" will reduce borer damage, even if conducted on a community-wide basis. For this reason, clean-up practices, such as clean plowing, stalk shredding, low cutting and ensiling, are recommended only to the extent that they are good cultural practices.
Insecticide Treatments
Corn borer can be controlled with insecticides provided they are correctly applied and at the right time. As a rule, one application will give satisfactory control of the first brood on field corn, but two or three applications might be needed against the second brood because egg laying extends over a much longer period of time. For this reason field corn in Indiana is seldom treated for control of the second generation borer. Treatment with insecticides is usually practical on market sweet corn, canning corn and hybrid seed fields. On field corn, treatment depends upon the degree of infestation.
FIELD CORN
When to Treat
When field corn reaches 35 inches tall (stretched-up leaf) it should be inspected every day or two to determine the percentage of plants that are infested. Infested plants have small "shot-holes" in the whorl and on the upper leaves. These holes are caused by the feeding of the recently hatched borers. An insecticide application is