Stink bugs and lady beetles coming in for the winter

As the days get shorter and colder, some insects gather on the sides of houses to find a sheltered place for the winter. Brown marmorated stink bugs, multicolored Asian lady beetles and boxelder bugs are the usual ones. They favor warm walls facing south or west. They squeeze through cracks and end up in the walls and attic until spring, and some make it into the living space. Stink bugs don't breed indoors over the winter, and they don't bite.

Sealing the house before they arrive is the best way to keep them out.

Which bug is it

• Brown marmorated stink bug. A large, flat, shield-shaped bug, mottled brown and gray, with white bands on the antennae and light triangles along the edge of the abdomen. Crushed, it leaves a stain and a smell like cilantro.
• Multicolored Asian lady beetle. Yellow-orange to red, with up to 19 black spots or none, and a black M behind the head. Disturbed, it gives off a bad smell and a yellowish fluid. Outdoors, it's a helpful insect.
• Boxelder bug. About half an inch long, black with red or orange lines, often found near boxelder and maple trees.

What you need

• A caulk gun and silicone or silicone-latex caulk
• Expanding foam, for larger gaps around pipes and wires
• Screen patches or replacement screen
• A vacuum, a knee-high stocking and a bucket of soapy water

Steps

1. 1

   Start before they gather

   Do the work before the bugs collect on the walls on warm fall days.

   5 min

2. 2

   Caulk the cracks

   Seal around the windows, doors, siding and utility pipes you can reach from the ground. Gaps as small as 1/8 inch let some insects in. Gaps behind the chimney, under the fascia or anywhere else up a ladder are a job for a contractor.

   60 min

3. 3

   Foam the bigger openings

   Fill larger gaps around pipes and wires where they go through the foundation.

   20 min

4. 4

   Fix the screens

   Repair or replace torn window and door screens, and check that windows and doors close tight.

   20 min

5. 5

   Check the eaves and soffits from the ground

   Look for gaps or damage in the siding, eaves and soffits. Close what you can reach from the ground, and leave the rest to a contractor.

   10 min

6. 6

   Vacuum up the ones that get in

   Put a knee-high stocking in the vacuum tube so the bugs collect in it, then empty it into a bucket of soapy water. Indoor insecticide isn't recommended for these bugs.

   5 min

7. 7

   Look for bugs inside on the next warm day

   Check around the windows and doors inside, and vacuum up any bugs you find.

   5 min

A professional spray outside

Where sealing the whole outside isn't possible, a pest control company can spray an insecticide on the outside walls as the bugs begin to gather. It gives some minor relief, and sunlight breaks it down within several days to a week.

Stink bugs in the garden

Unlike lady beetles and boxelder bugs, brown marmorated stink bugs are more than a nuisance. In summer they feed on tree fruits, vegetables and ornamental plants, and can do a lot of damage. If you're not sure which bug you have, the county extension office can identify it.