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Stink Bug Damage Reported in Some Cornfields

June 14, 2002
Duane Frederking, an agronomist with Pioneer Hi-Bred International Inc., reported that several cornfields near Beardstown, Cass County, were infested with stink bugs. Infestation levels ranged from 5% to 10% of plants affected. Onespotted and brown stink bugs can be found throughout the North American continent; however, they are especially common in the Midwest. Both species are very similar in appearance and are easily recognized as brown, shield-shaped insects, measuring 2/5 to 3/5 inch in length and roughly 1/3 inch in width. Onespotted male stink bugs display a dark spot on the undersurface of the abodomen near the wing tips. Not all stink bugs injure crops. The spined soldier bug looks very similar to the onespotted and brown stink bug species. Spined soldier bugs are predaceous and are therefore considered beneficial insects. Predaceous stink bugs have thicker and stouter mouthparts than their plant-eating "relatives." All stink bugs undergo incomplete metamorphosis, with the immatures or nymphs undergoing several moults (five instars) before reaching the adult stage. The nymphs do not have fully developed wings and display some eye-catching flashes of orange, yellow, and green against a black body. Stink bugs may complete one to three generations per year (latitude dependent), with a complete life cycle requiring 6 to 8 weeks.

Onespotted and brown stink bugs spend the winter beneath vegetation found growing near cultivated fields. Overwintering vegetation may include alfalfa, wheat, or rye cover crops. Stink bug injury to corn is generally favored following a mild winter. Corn that has been planted into a wheat or rye cover crop is more susceptible to economic problems. Both nymphs and adults insert their needlelike mouthparts into the tender stems of corn plants, thereby introducing enzymes into the vascular system of young plants. These compounds can elicit phytotoxic symptoms and/or lead to growth abnormalities, such as "suckering" or profuse tillering. Other symptoms on plants may include the presence of very small feeding holes surrounded by yellow or decaying plant tissue. Severely injured plants may become stunted, wilted, and subsequently die. Stink bug injury limited to even 1 day of feeding has been reported to cause significant yield reductions. Fields most likely to support economic infestations of stink bugs include those fields with seed slots that have not been closed properly. This often occurs when fields have been planted too wet and/or the planter settings have not been adjusted to match field conditions.

Thresholds have not been developed for stink bug injury to corn. Thresholds that have been developed for cutworms have been used to assist in the decision-making process on occasion. Insecticides that are labeled as rescue treatments for stink bug infestations in corn include *Capture 2EC (2.1 to 6.4 ounces of product per acre), *Penncap-M (1 to 3 pints of product per acre), and *Warrior (2.56 to 3.84 ounces of product per acre). These products are restricted-use insecticides and may be applied only by certified applicators.--Mike Gray

Scouting a cornfield (corn planted no-till into a cover crop) infested with stink bugs.

Stink bug on corn plant.

"Dead-heart" injury caused by stink bug feeding.

Stink bug injury to vascular tissue of corn plant.

Author: Mike Gray

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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