Brown Marmorated Stink Bugs in Soybean

The brown marmorated stink bug is an invasive species that was inadvertently introduced from Asia to the U.S. in the 1990’s. Since that time, it’s impact on crops, especially in the mid-Atlantic region, has increased.1 Stink bugs overwinter in leaf litter, crop residue, and other plant debris and feed on the fruits and seeds of a wide range of plants including corn and soybeans.

Brown marmorated stink bugs are shield-shaped insects in mottled shades of brown and gray and are covered with dense puncture marks on the upper side of the body (Figure 1). The underside of the body is white, sometimes with gray or black markings. They have dark red eyes and the legs are brown with faint white banding. Broad light and dark bands on the last two antennal segments distinguish brown marmorated stink bugs from other stink bugs.

 

Figure 1. Brown marmorated stink bug. Photo source: Susan Ellis, Bugwood.org.

Stink bugs feed by inserting their piercing-sucking mouthparts into plant tissues and extracting plant fluids. Enzymes that are transmitted from the mouthparts into plant tissues can cause growth abnormalities and cause plants to become more susceptible to other stress factors such as drought, disease, or attacks by other insect pests.2,3 Stink bugs prefer to feed on young, tender soybean pods and developing seeds during the R5 to R6 stages of growth.4 Feeding can cause deformation and abortion of the pods and seeds within the pods, resulting in potential yield reduction (Figure 2). Additionally, feeding can reduce seed quality, oil content, and germination. Young seeds become deformed, while older seeds may be discolored and shriveled.

 

Figure 2. Damage to soybean pods and seeds by stink bugs. Photo Courtesy of Ric Bessin, University of Kentucky.

Soybean plants have some ability to compensate for minor stink bug damage by reallocating photosynthate from the damaged seeds to the undamaged seeds within the plant, thus increasing the weight of undamaged seeds.4 Under heavy stink bug feeding, however, soybean plants divert that photosynthate into vegetative tissues.4 When this occurs, soybean stems may retain their greenness beyond pod maturity which can delay harvest and lead to potential yield loss.5

Stink bug damage to corn and soybean fields may be initially noted on the field borders as the insects colonize the outside edges and eventually move into the field.1,3 In soybean, pod establishment and elongation (R3-R4) through seed fill (R5.5) are the critical growth stages for considering insecticide treatments.4 If stink bug populations reach economic thresholds, an insecticide application may be warranted. Damage to crops may be most severe near tree lines, and field perimeter treatments may be used to temporarily stop a stink bug invasion. Such treatments likely will limit the insect for only a short time as adult stink bugs are strong fliers and can move in and out of fields as well as move farther into the field. Check with local university Extension for products approved and recommended for stink bugs in your region.

Sources: 1 Tooker, J. 2012. Brown Marmorated Stink Bug as a Pest of Corn and Soybeans. Penn State College of Agricultural Sciences. Insect Advice from Extension. http://ento.psu.edu/extension/factsheets/; 2 Hunt, T., Wright, B. and Jarvi, K. Stink bugs reported in corn and soybeans. CropWatch. University of Nebraska-Lincoln Extension; 3 Michel, A., Bansal, R. and Hammond, R.B. 2015. Stink bugs on soybeans and other field crops. Ohioline. Ohio State University Extension. 4 Hooks, C.R.R. 2011. Stink bugs and their soybean obsession. University of Maryland. Agronomy News. Vol. 2, Issue 9; 5 Egli, D.B. and Bruening, W.P. 2006. Depodding causes the green stem syndrome in soybean. Plant Management Network: Crop Management. Web sources verified 10/09/17. 171009214730