Stink bugs are on the rise in soybeans. They are commonly a problem in vegetable crops such as lima beans and tomatoes. However in recent years we have seen build ups in soybeans.
From Joanne Whalen, UD IPM Extension Specialist in the Weekly Crop Update:
We have started to see an increase in populations of both green and brown stinkbugs. You will need to continue to scout for stinkbugs in fields that are in the pod development and pod fill stages. Economic damage is most likely to occur during these stages. You will need to sample for both adults and nymphs when making a treatment decision. Available thresholds are based on beans that are in the pod development and fill stages. We are currently following the same guidelines that are being used in Virginia. Thresholds are based on numbers of large nymphs and adults, as those are the stages most capable of damaging pods. As a general guideline, current thresholds are set at 1 large nymph/adult (either brown or green stink bug) per row foot if using a beat sheet, or, 2.5 per 15 sweeps in narrow-row beans, or 3.5 per 15 sweeps in wide-row beans. Since we have not done any research on stinkbug control, here is what Ames Herbert from VA indicated in his last newsletter: “Our research and others shows that brown stink bugs can be more difficult to kill with pyrethroids. If faced with a bad brown stink bug problem in soybeans, Orthene 97 at 8 oz/acre offers the best solution. For a lesser problem, a medium to high pyrethroid rate will do a lot.”
More on stink bugs from a fact sheet from the University of Missouri Extension modified for Delaware conditions:
In Delaware, the green stink bug, Acrosternum hilare (Say), and brown stink bugs, Euschistus spp., commonly infest soybean fields. Throughout North America, the green stink bug is tied for second among all insect species attacking soybean pods and seeds. Stink bugs are typically more of a problem in the southern states than in northern states. In Delware, we are seeing increases in stink bug feeding in soybeans in the last few years.
Stink bug at a glance
>Stink bugs produce a foul odor in self-defense.
>Both brown and green stink bugs attack both soybean pods and seeds.
>Stink bugs have piercing-sucking mouthparts that act like hypodermic needles to remove the plant’s fluids.
>Stink bugs affect the quality of soybeans by damaging seeds, yield by piercing seeds and causing seed abortion or reduced seed size, and in severe cases can cause pod drop (very high numbers piercing pods).
Description and life cycle
Stink bugs overwinter as adults underneath leaf litter, tree bark, and other materials in areas not used for crops. When spring time temperatures begin to increase, stink bugs become active and begin feeding on both cultivated and wild host plants. Adult green stink bugs are bright green with black bands on their antennae. They differ from southern green stink bugs, Nezara viridula (L.), by having a pointed (not rounded) spine between their hind legs. Adult brown stink bugs are brown with yellow to light-green undersides. They should not be confused with the spined soldier bug, Podisus maculiventris (Say), a predaceous stink bug species that also is brown and has a cream-colored underside. Spined soldier bugs differ from brown stink bugs by having more pronounced spines on their pronotum (shoulders), a black spot on their abdomen, and reddish legs.
Once overwintering adult stink bugs rebuild their energy reserves, they mate, and females begin laying their eggs in early summer. Females lay tight clusters of 10 to 30 barrel-shaped eggs on soybean plants. Depending on weather conditions, the nymphs will hatch within one to three weeks. The first-instar nymphs (the green stink bug is reddish brown; the brown stink bug is yellow to tan) do not feed and remain clustered on their egg masses. The green stink bug nymphs (second- and third-instars) are pale to dull green with black and white strips. Later instar nymphs are green with yellow and black strips or a pale, yellow-green color with black markings. All brown stink bug nymphs are yellow to tan with brown spots down the middle of their abdomen. Depending on the species and weather conditions, it takes between 23 days and two months to progress from the egg to adult stage. Depending on the species, stink bugs annually will have one to three generations in Delaware.
Both the nymphal and adult stages attack primarily the seeds and pods of soybean plants. They also will feed on soybean plant stems, foliage, and blooms. Usually the location of feeding punctures can be identified by the presence of small brown or black spots. Direct feeding damage can lead to a reduction in seed quality and quantity. Young seeds can be deformed, undersized or even aborted, whereas older seeds will be discolored and shriveled. The germination rate also will be reduced for beans produced as a seed source. Indirectly, feeding damage by stink bugs can delay plant maturity and cause the abnormal production of leaflets and pods. This condition is referred to as the “green bean effect.” For example, southern green stink bugs cause the most damage from the time soybean seeds begin to develop until they begin to fill.
Extracted and modified from:
Soybean Pest Management: Stink Bugs
Michael L. Boyd and Wayne C. BaileyState Extension Entomology Specialists
University of Missouri