Brown Stink Bug in Soybean
Crop Damage
Brown stink bugs (Euschistus spp.) represent a group of over 20 species that occur throughout the United States and Canada. They have a broad host range that includes corn, wheat, and soybeans. Both nymphs and adults use their piercing-sucking mouthparts to feed on soybean leaves, stems, flowers, pods, and seeds. As they feed, they inject digestive enzymes that damage plant tissue and expose the area to pathogens. Brown stink bugs cause the greatest economic damage when they feed on developing pods and seeds, which can result in shriveled seeds and reduced seed size.
Description
Young nymphs are greenish-brown with distinct brown spots on the abdomen. As they mature, older nymphs turn light green and develop a distinctive brown, triangular marking on the abdomen. The wing pads have a characteristic pitted appearance. Adult brown stink bugs are approximately 1/2 inches long and are grayish-brown with numerous dark punctures on their back. Unlike many other stink bug species, the shoulders (also known as the pronotum) are rounded rather than sharply pointed.
Brown stink bug nymphs.
Herb Pilcher, USDA ARS, Bugwood.org.
Brown stink bug nymph. The black arrow indicates the brown triangle on the abdomen. The blue arrow indicates the wing pads with a pitted surface.
Herb Pilcher, USDA ARS, Bugwood.org.
Scouting
There are various scouting protocols and management thresholds based on the seasonal movement, abundance, and potential damage caused by brown stink bugs. Depending on the state, scouting is recommended when soybeans begin blooming (Stage R1) and may continue until full maturity (Stage R8). Sweep nets and drop cloths are two common tools used to monitor brown stink bug populations. When using a sweep net, take 25 sweeps in 4 locations within the field. Larger fields may require additional sampling locations to obtain an accurate estimate of stink bug populations. Count the number of older nymphs and adults. When using a drop cloth, place a 6-foot-long white sheet between two rows and shake all the plants on one side towards the sheet in 5 to 8 locations in a field. Count the older nymphs and adults that land on the sheet and determine the average number per row foot.
Brown stink bug adult. The black arrow indicates the rounded pronotum.
Herb Pilcher, USDA ARS, Bugwood.org.
Management
Common insecticide treatment thresholds for stink bugs when using a sweep net are 9 stink bugs per 25 sweeps (40 stink bugs per 100 sweeps) for grain production fields and 5 stink bugs per 25 sweeps (20 stink bugs per 100 sweeps) in seed production fields. Drop cloth treatment thresholds are 1 stink bug per row foot for grain production fields and 1 stink bug in the six-foot row for seed production fields.
Timing of scouting and insecticide treatment thresholds vary by state, so consult with local or state extension specialists for current scouting and treatment recommendations. If multiple stink bug species are present, assess their potential impact before making management decisions. If treatment is warranted, consider the pre-harvest interval (PHI) when selecting an insecticide for late-season applications. In some areas, reduced efficacy of pyrethroid insecticides against brown stink bugs has been reported, so determine local recommendations when selecting a product.
Developed and reviewed by Carol Pilcher, Iowa State University and Robert Wright, University of Nebraska-Lincoln, with support from the United Soybean Board.
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