Biology

Stink bug (Hemiptera: Pentatomidae) populations have been increasing in soybean fields in Missouri. These insects have piercing mouth parts and feed on blooms, pods, and developing seeds within pods. Stink bugs can cause significant yield losses and reduce seed quality. Their populations usually increase during soybean reproductive growth stages. Adult stink bugs move from the field edges and are often more numerous at the field margins during the colonization period. Female lay eggs in masses, and after hatching, young nymphs remain in the same area during their first instars. When nymphs reach the fourth and fifth instars and adult stages, they move throughout the soybean fields.

In Missouri, three stink bug species are commonly found in soybean fields: the green stink bug, Chinavia hilaris the one-spotted stink bug, Euschistus variolarius, and the brown stink bug Euschistus servus. These three species overwinter as adults and emerge from diapause during the spring when temperature and day length increase. Our ongoing sampling efforts across central, northeast, and northwest Missouri have found the green stink bug as the most abundant species so far.

Figure 1 Adult stink bugs on soybeans.

Species identification

Stink bugs vary in shape and size and are generally described as shield-shaped bodies. Adult green stink bugs are usually light green and are 13 to 19 mm long. Nymphs are oval-shaped and range in size from 1.6 to 12.7 mm. The eggs are barrel-shaped, change from light green to yellow, and are usually found on the underside of leaves.

Figure 2 Green stink bug eggs(A) and nymphs(B).

One-spotted stink bug adults are yellowish-brown and 11 to 15 mm long. Males have a large black spot on the underside, near the tip of the abdomen. One-spotted stink bugs and brown stink bugs are very similar. Apart from the absence of a black spot on the abdomen of the adult male, brown stink bug adults have more rounded shoulders than one-spotted stink bug. The eggs of both species are yellowish-translucent and barrel-shaped.

Figure 3 One-spotted stink bug adult(A) and eggs(B).

Scouting and insecticide management

Stink bugs scout should begin when soybeans start to bloom. Because stink bugs tend to aggregate in certain areas of the field, it is important to sample multiple points to get an accurate assessment. A sweep net can be used to check stink bug densities in soybean fields. Current management recommendations are based on scouting and threshold levels. When using a sweep net, the threshold is 8 stink bugs per 20 sweeps in production soybeans and 4 per 20 sweeps in seed beans.

More information on stink bugs biology, species identification and management can be found at: https://academic.oup.com/jipm/article/8/1/11/3745633.