- Reports indicate that stinkbug populations are elevated in some areas
- Stink bugs can cause yield loss and reduced seed quality in soybeans.
- Scout for stink bugs using a beat cloth or sweep net during growth stages R1 to R5.
General information
Stink bugs have become increasingly common late-season pests in soybeans. Stink bugs are shield-shaped insects and may emit an offensive odor if handled. Stink bugs go through gradual metamorphosis, meaning that the immature developmental stages, or nymphs, are smaller versions of the adult insect. There are many species of stink bugs, but the species most commonly found in Midwest soybeans include the brown stink bug, the brown marmorated stink bug, and the green stink bug (Image 1). Eggs are barrel-shaped and found on the underside of the soybean leaf (Image 2). The immature nymphs resemble the adults, but lack fully developed wings and often vary considerably in color (Image 3). Less experienced field scouts may sometimes misdiagnose the nymphs as a different species of insect.
Image 1. Green stink bug adult. (Source:GROWMARK, Inc.)
Image 2. Green stink bug egg mass on the underside of a soybean leaf . (Source:GROWMARK, Inc.)
Image 3. Green stink bug nymphs on a soybean pod (Source:GROWMARK, Inc.)
Stinkbug Damage
Elevated numbers of stink bugs can yield and quality loss in soybeans. Stink bugs feed with piercing-sucking mouthparts on tender stems, petioles, and the developing beans. These mouthparts puncture and damage tissues and also are used to inject enzymes to aid in digestion and material removal. These actions can cause shriveled, small soybeans if pods and beans are targeted. In addition, seed germination may be reduced, even if seed appears healthy.
Scouting and Thresholds
Stink bugs populations typically increase from mid-July through harvest. Scout soybeans for stink bugs in growth stages R1 through R5. Adults tend to aggregate in sections of the field, so rigorous sampling over several areas of the field may be needed for an accurate assessment. Keep in mind that samples from near woods or fence rows may have higher counts. Scouting should focus on both adults and late instar nymphs. A beat cloth may be useful to scout 30-inch rows, whereas a sweep net may be more convenient in narrow rows.
A generally accepted threshold for stink bugs in soybeans is 1.0 per linear foot of row for commercial soybeans or 0.5 per foot of row in seed production. The thresholds should be considered dynamic and may be adjusted to reflect the presence of other late-season insects and market economics.
Management
Most insecticides labeled for use on soybeans will provide effective stink bug control. Insecticides with neonicotinoid active ingredients also provide systemic activity, which may be an advantage for insects like stinkbugs that feed with piercing-sucking mouthparts. Be cognizant of pre-harvest intervals (PHI) when applying insecticides later in the growing season. Always read and follow label directions.