• Stink bugs can cause economic injury to corn, especially when no-till planting into cereal residues, cover crops, or grassy weeds.
• Typical stink bug injury is a repeated pattern of elongated holes across the leaf with characteristic yellow halos or streaks.
• Additional symptoms include distorted growth, stunting, tillering, and deformed ears.
• The most effective control method in high risk environments when insects are present is a preventative insecticide applied with burn down herbicide before planting.
• Seedling corn is most vulnerable during the first two weeks after emergence.  If stink bugs are present on 10% of plants, consider one of the following foliar insecticides as a rescue treatment:  Baythroid® XL, Cobalt® Advanced, Fastac® EC, Hero EC, Mustang® Maxx, Stallion™, Warrior II with Zeon Technology®.

Biology
Several different species of stink bug are known to cause injury to corn, but most common is the brown stink bug.  They are brown in color, about ½" long, broad, flat, and shield-shaped, with sharply pointed corners on the pronotum.  They release a strong odor when handled or crushed.  Brown stink bugs overwinter as adults in wooded areas, grass borders, winter cover crops, weedy fields, or cereal crop residues.  This overwintering generation emerges and begins feeding in these habitats.  Mating occurs in early spring and eggs are deposited about a month later.  The entire life cycle from egg to adult is a little shorter than two months.  Nymphs emerge and may be found alongside the overwintered adults in the same crop.  Stink bugs can survive on a wide array of plant and weed species.  When cover crops or weeds are burned down prior to planting, stink bugs will seek other food sources, such as emerging corn.   

Injury
Stink bugs feed by inserting 'stylete' feeding tubes into the plant tissue and extracting plant juices.  They inject an enzyme that solubilizes plant tissue to aid in feeding, but this material has a toxic effect on the plant, causing chlorosis, distorted growth, and stunting.  Seedling corn is most vulnerable to severe injury.  As leaves of the whorl unfurl, the single feeding site injury appears as a series of holes across the leaf surface, each with a characteristic yellow halo.  As the plant grows, the holes elongate into an oblong shape, with chlorotic zones extending out parallel with the leaf.  Tissue surrounding the injury is often deformed and may have a crinkled appearance.  If the growth point is injured, the plant may become severely deformed and not recover.  About 10 days after the initial injury is evident, plants may begin to tiller or sucker and these tillered plants may not produce viable ears.  Stunted plants may recover in 2-4 weeks, with about 10% expected yield loss.  In conventional fields, injury is scattered and rarely economic, but in no-till fields damage patterns can be somewhat uniform and yield losses significant.  Later planted corn is often more vulnerable to attack and should be scouted more closely. 

Scouting and Management
In high risk no-till environments like those described above, scouting needs to start well ahead of planting.  If stink bugs are found in weeds or cover crops, a preventative insecticide application may be warranted with the burn down herbicide application.  Aggressively scout during the first 2 weeks after corn emergence.  Stink bugs tend to feed about an inch above the ground, so look for actual insects in the whorl, on the base of the plant, on the ground, and in residue around the plant.  If early stage shot-hole injury is detected, check whorls.  The insects are mobile and are often not found in the injured plant, but have moved on to a neighboring plant which is showing no injury.  Thresholds vary due to a general lack of understanding about the extent of injury from this pest.  If scouting reveals 1 bug per 10 plants, consider a foliar rescue treatment using the highest labeled rate of any of the following major corn foliar insecticides:  Baythroid® XL, Cobalt® Advanced, Fastac® EC, Hero EC, Mustang® Maxx, Stallion™, Warrior II with Zeon Technology®.  Because stink bugs often take refuge in the whorl, control may be difficult without adequate volume and coverage.  If injury symptoms are advanced on corn less than 24 inches, the stink bugs and the window of opportunity for treatment are probably both long gone – focus then should shift to prevention for next growing season.  Stink bugs may also be a persistent problem throughout the growing season, attacking the developing ear in late whorl and early reproductive stages.

Always read and follow insecticide label directions.  Always apply Integrated Pest Management principles for treatment decisions.

Contact your FS Crop Specialist for your agronomic information.

Reference: 
Brown Stink Bug (Purdue University)