Dusky Stink Bug Identification Guide

Dusky Stink Bug Identification Guide

Physical Characteristics

The dusky stink bug (Euschistus tristigmus) is a shield-shaped insect in the stink bug family. Adults are about 9-15 mm long, making them a bit smaller than the brown marmorated stink bug. Their color ranges from dull brown to grayish-brown. This helps them blend in with tree bark, soil, and dead leaves.

You can spot dusky stink bugs by their pointed shoulders. They have small, sharp points on each side of the area behind their head. The back shows dark speckles, while the wings have lighter patches. The belly is light-colored with dark spots near the rear. Their legs and antennae are plain brown without any bands or stripes.

Subspecies

There are two types of dusky stink bug: Euschistus tristigmus tristigmus and Euschistus tristigmus luridus. Both are native to North America and look and act alike. They may differ slightly in color depending on the region.

Eggs and Nymphs

Female dusky stink bugs lay barrel-shaped eggs in clusters on the undersides of leaves. The eggs start out pale green to yellow. They darken as the bugs inside grow. Young stink bugs, called nymphs, go through five growth stages before becoming adults. Young nymphs are smaller and may look different from adults. They slowly develop the brown color and shield shape as they grow. Nymphs cannot fly because their wings are not fully formed. They stay on plants until they become adults.

Dusky Stink Bug Behavior and Biology

Lifecycle and Reproduction

Dusky stink bugs grow from egg to nymph to adult without a cocoon stage. Adults spend winter in sheltered spots like fence rows, under dead weeds, beneath stones, or in tree bark. They wake up on the first warm days of spring. You might see them as early as when fruit trees bloom.

This species has two generations per year in most areas. The first group is most active from May through June. Activity drops in July. A second generation appears in late July through August. These adults look for winter hiding spots as fall arrives.

Feeding Habits

Dusky stink bugs have mouth parts that pierce and suck. They push a needle-like tube into plants to drink the fluids inside. Both adults and young bugs eat many types of plants. Common targets include beans, tomatoes, corn, soybeans, cotton, and fruit trees.

Their feeding causes damage that is easy to spot. You may see discolored seeds, misshapen fruit, and wilting leaves. On fruits like peaches and apples, feeding during bloom can make fruit fall off. Later in the season, feeding leaves dimpled or sunken spots on the fruit skin.

Overwintering Behavior

When temperatures drop in fall, adult dusky stink bugs look for shelter to survive winter. Unlike the brown marmorated stink bug, which can invade homes by the thousands, native dusky stink bugs usually spend winter outdoors. But they may still get inside through gaps and cracks. This is more likely if your home is near farms or wooded areas.

Adults remain dormant throughout winter and do not feed or reproduce. If temperatures rise during a winter warm spell, these stink bugs may wake up and move around briefly.

How We Treat for Dusky Stink Bugs

Dusky stink bugs are mainly a nuisance pest. The best approach is to focus on prevention rather than waiting until they are inside. Sealing entry points and applying treatments at the right time gives the best results.

Preventative Exterior Treatments

Before the weather turns cold in fall, usually around October, our technicians apply dust treatments to exterior voids. These are spots where stink bugs often enter and hide. We target weep holes in brick, gaps behind siding, and spaces around windows and doors. This creates a barrier that keeps insects out. We also treat the outside perimeter with a repellent to stop stink bugs from gathering on walls and foundations.

Exclusion and Sealing

Sealing entry points is the best long-term way to keep stink bugs out. Here are key steps:

• Seal cracks with silicone caulk
• Replace worn weatherstripping around doors and windows
• Install door sweeps
• Cover attic vents, exhaust fans, and chimney openings with fine-mesh screens

Fixing these entry points keeps out stink bugs and other pests that try to get inside for winter.

Interior Treatments

If stink bugs have already gotten inside, we apply repellent treatments around window seals, door frames, and baseboards. In bad cases, we may need to dust inside wall voids. Once large numbers settle inside, getting rid of them all can be hard. That is why fall prevention matters so much.

What Homeowners Can Do

For stink bugs already inside, vacuuming is the easiest way to remove them. Use a shop vac or set aside a vacuum bag just for this task to help contain the smell. Do not crush stink bugs. Crushing them releases a bad odor and may stain surfaces. Put the bugs you collect in soapy water outside.

Removing plants that attract stink bugs from near your home can also help. Focus on broadleaf weeds and legumes. Fewer host plants nearby means fewer stink bugs trying to get inside.

References

• Euschistus tristigmus - Wikipedia
• Dusky Stink Bug - Michigan State University Extension
• Stink Bugs - Virginia Tech Fruit Entomology
• Look-Alike Insects - StopBMSB.org
• Field Guide to Stink Bugs - USDA ARS