Brown Marmorated Stink Bug

What it looks like

• Shield-shaped body, ~5/8" long
• Mottled gray-brown with white bands on the antennae
• Alternating light and dark bands on the edge of the abdomen
• Strong unpleasant smell (like cilantro mixed with skunk) when disturbed or crushed

Where you'll find it

• Fruit trees, garden vegetables, and ornamental plants in summer
• South and west-facing siding in fall
• Attics, wall voids, and behind exterior trim (overwintering)
• Indoor lights and warm window panes on winter days

Behavior & biology

Brown marmorated stink bug (BMSB) is an invasive species from Asia, first detected in the US in the 1990s. It's spread to most states including Iowa. Adults feed on fruit, vegetables, and ornamentals — causing major agricultural damage in apple and peach orchards. In fall they migrate to buildings to overwinter, often in massive numbers. They emit a strong defensive odor when disturbed.

Iowa activity calendar

Signs of an infestation

• Shield-shaped brown bugs on south-facing siding in fall
• Indoor sightings on warm winter days, especially on south-facing windows
• Strong unpleasant smell when disturbed or vacuumed
• Damaged fruit and vegetables in summer (small dimpled spots)

Health & property risk

Major agricultural pest. In homes: nuisance and smell only — no bites, no structural damage, no human health concern.

How we treat it

1. 1

   Late summer perimeter treatment

   August-September exterior treatment on south and west walls — same approach as boxelder bugs and Asian lady beetles. These three pests are typically treated together.

2. 2

   Cluster spray

   Direct spray during peak fall clustering reduces indoor pressure.

3. 3

   Seal entries

   Caulk gaps around utility penetrations, window frames, and soffits.

4. 4

   Vacuum indoor bugs

   Use a stocking over the vacuum nozzle to capture without sucking them through (the smell). Release outside or freeze the stocking before disposing.

Why DIY usually fails

Don't squash them — the smell lingers. Vacuum gently and dispose outside. Caulking and exterior treatment in late summer are the only effective preventive steps.

FAQ