Field Corn
Southwestern Corn Borer
Frank B. Peairs
Southwestern Corn Borer
Identification (and life cycle/seasonal history)
Southwestern corn borer 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? inches) long. Moths are white to pale yellow in color and about 19 millimeters (? inch) long. They have no dark markings. Adults are active primarily at night but can be found during the day under leaves.
Over wintering 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 can be anywhere from two to three generations of southwestern corn borer per year. Generally, eggs 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
The first brood of Southwestern corn borer causes dead heart by destroying the growing point of young plants. 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 rootworm events. See Managing Corn Pests with Bt Corn, http://www.ext.colostate.edu/pubs/crops/00708.html, for details on the use of Bt corn hybrids to control corn pests.
Product list for southwestern corn borer
RRestricted use pesticide. 1Labeled for chemigation. 2Generic active ingredient, may be additional formulations. |
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The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
Categories: Field corn, Insects, Southwestern corn borer
Date: 5/16/2008