HPIPM:Southwestern Corn Borer FC

Author: Frank B. Peairs[1]

Identification (and life cycle/seasonal history)

Southwestern corn borer, Diatraea grandiosella Dyar, larvae are dull white with dark brown to black spots forming a regular pattern along the body. These spots generally disappear in over wintering larvae. Fully developed larvae are 25 to 32 millimeters (one to 1.2 inches) long. Moths are white to pale yellow in color and about 19 millimeters (0.75 inch) long. They have no dark markings. Adults are active primarily at night but can be found during the day under leaves.

Overwintering larvae pupate in the spring and emerge as adults about 10 days later. These moths lay eggs that produce the first generation of southwestern corn borers. There are two to three generations per year. Generally, eggs, which have distinctive red bands, are laid in groups of two to five, overlapping slightly on the upper surfaces of leaves.

Plant Response and Damage

Young larvae feed in the whorls of young corn plants. This feeding may result in "dead heart," the death of the growing tip. Half-grown larvae of the second or third generation crawl down from the whorl and burrow into the stalk and begin tunneling in preparation for over wintering. The larvae chew a groove around the inside of the stalk a few inches above the soil surface. This girdling weakens plants and makes them susceptible to lodging. The mature larva over winters in the underground part of the crown of the corn plant.

Management Approaches

Second brood larvae girdle stalks, which often results in lodging. Early planted corn may escape second brood damage. Early varieties and crop rotation may also reduce yield losses. Fall and winter stalk destruction, on an area wide basis, can reduce over wintering populations. If 25 percent of the plants have egg masses or newly hatched larvae, chemical control is justifiable.

Control can be expected with Bt corn hybrids, except those containing just events that target corn rootworms. See Managing Corn Pests with Bt Corn, [2], for details on the use of Bt corn hybrids to control corn pests. See [3] for an excellent summary of currently available traits.

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.