May 7, 2010

Historically, stink bugs have not been a significant pest in Nebraska, but in recent years there have been more frequent reports of damage to corn in Nebraska and areas of the north central U.S.

Stinkbugs can injure seedling corn, reproductive stage corn and reproductive stage soybean. We will discuss stinkbugs on seedling corn in this article.

Little research-based information on stink bugs is available for the northern part of their range, which includes Nebraska. The following information is derived from our recent research on stink bugs in Nebraska (work funded by the Nebraska Soybean Board) and pertinent information gleaned from other states (e.g. Missouri, Virginia).

Description

The major stink bug species that feed on seedling corn in Nebraska are the brown stink bug, Euschistus servis (Figure 1), and the one-spotted stink bug, Euschistus variolarius. Adult brown stink bugs are brown with a yellow or light green underside. Brown stink bug nymphs (immature stink bugs) are yellow to tan with brown spots down the center of the abdomen. The one-spotted stink bug looks similar to the brown stink bug, except it has a small spot on the underside of the abdomen. Another brown stink bug, the spined soldier bug, Podisus maculiventris (Figure 2), is a beneficial predatory insect.

General Biology

In Nebraska we have observed adult brown and one-spotted stinkbugs in alfalfa prior to and during corn planting and emergence. These likely overwinter in Nebraska, begin feeding in alfalfa or small grains in early spring, and then migrate to corn as it emerges. They appear to survive the winter in leaf litter, under bark, or in wood piles. In the spring, adult stink bugs leave the overwintering sites and feed on a variety of wild and cultivated hosts. After feeding a few days, stink bugs mate and lay clusters of eggs. As the season progresses, female stink bugs are attracted to a variety of flowering plants. There are likely at least two generations in Nebraska each year.

Injury to Seedling Corn

Stink bugs insert their needle-like mouthparts into the base of seedling corn plants to inject salivary enzymes into the plant. These enzymes help stink bugs feed on the plant tissue. Depending on the plant stage attacked, injury symptoms may include death of the growing point, leaf distortion and twisting of the plant, yellow streaks or holes in the leaves as they emerge from the whorl, and tillering.

Previous observations indicate that fields where the seed furrow was not fully closed due to planting during wet field conditions may favor injury by stink bugs by allowing access to the plant’s growing point below ground. Often injury appears first on the field border as the stink bugs move into the field. If damage is observed soon enough, it may be possible to only treat the field border. With time the stink bugs can move throughout the field.

Management

There is no published research to establish an economic injury level or threshold for stink bugs on seedling corn; however, we have compiled the following information to aid in decision making.

Scouting

• The two weeks after corn emergence is a critical period to watch for stink bug damage. Feeding may start 10 to 20 days before clear symptoms of injury (twisting, stunting, wilting or plant death) are present, so early scouting is critical.
• Stink bug problems may be more likely in late planted fields and no-till fields. Corn next to alfalfa also may be more vulnerable.
• Scout the field as you would for cutworms. In addition to looking for cut plants (cutworm activity), look for stink bugs and their damage. Look near the base of plants, on leaves, at leaf nodes and in the whorls and remember that stink bugs hide low during the day or when it’s windy.
• One indication of stink bug damage is a line of oval holes, often surrounded by a yellow border, across the leaves as they grow out of the whorl.
• Plants along a row may exhibit a progression of symptoms, giving a stair step appearance (dead plants, stunted plants, tillering plants).
• Be sure to positively identify the source of damage as other insects (e.g. wireworm, billbug) can cause similar injury to stinkbugs.

Treatment

Several thresholds have been published for stink bugs on seedling corn. Prior to injury in corn less than 24 inches tall, consider treatment if 10% or more of plants are infested with stink bugs. With injured plants, we suggest a postemergence threshold of when 3-5% of the plants have injury and stink bugs are present.

The following products are labeled in Nebraska for stinkbug:

• Warrior with Zeon Technology (lambda-cyhalothrin) — 2.56-3.84 fl oz per acre
• Proxis (gamma-cyhalothrin), 2.56-3.84 fl oz per acre
• Mustang MAX EC (zeta-cypermethrin) — 2.72-4.0 fl oz per acre
• Delta Gold (deltamethrin) — 1.5-1.9 fl oz per acre
• Hero (zeta-cypermethrin + bifenthrin) — 4.0-10.3 fl oz per acre
• Penncap-M (methyl parathion) — 1-3 pints per acre

Tom Hunt
Extension Entomologist, Haskell Ag Lab, Concord
Bob Wright
Extension Entomologist, Lincoln
Keith Jarvi
Extension Educator, Thurston, Dixon, and Dakota Counties