Western Conifer Seed Bug

Western Conifer-Seed Bug

Scientific Name: Leptoglossus occidentalis
Also known as: WCSB
Pest type: Fall invader

Western conifer-seed bugs (WCSB) are overwintering pests that live outside during the summer and feed on pinecones. In the fall, they enter structures for protection against the cold and desiccating wind. Like other overwintering insects, they do not build a nest indoors or cause structural damage, but rather hide in cracks and crevices. They may be seen on warm winter days near windows during the day and lights at night.

Appearance

Western Conifer Seed Bugs are ‘true bugs.’

Distinctive Features: sucking mouthparts • a triangular ‘shield’ where wings overlap near the • A dark “X” across the back • fancy flairs on their hind legs •alternating dark and light markings along the outer sides of the body
Size: 3/4 inch (19mm)
Color: mottled dark browns

Western conifer seed bugs are often confused with brown marmorated stink bugs but are longer and narrower.

Long, shield shaped brown insect with yellow and black abdomen pinned to a white background and labeled with triangular shield, X across the back, dark and light markings along side of body, and flair on hind legs

Often confused with:

Brown Marmorated Stink Bug

Cornell University Insect Diagnostic Laboratory

Western Conifer Seed Bugs (pdf)

Should I Worry About Western Conifer-Seed Bugs?

While a heavy presence of WCSB can damage conifer seeds, their habit of overwintering inside homes makes them a nuisance. These insects do not bite or sting and so far, there’s no evidence they cause allergic reactions. They do not carry disease, but no one likes the strong, lingering odor emitted when they are disturbed. They are not stink bugs but they can stink!

Overwintering insects inside structures often die before spring leaving behind their bodies, which may attract and feed other incidental pests, such as carpet beetles and silverfish.

Why Do I Have Western Conifer-Seed Bugs in My Home?

You won't find WCSB nymphs in your home. Only the adult life stage overwinters in New York.

Adults and nymphs feed on conifer seeds (think pine cones), so your chance of having them around depends on the nearby landscape. You may never see them on trees, but you will notice them when they gather to overwinter inside structures such as houses or are active indoors during the winter. They are adept at finding entry through any gap in siding, eaves, and openings around doors and windows. Their noisy, bumbling flight inside your home makes them hard to miss.

How Do I Manage Western Conifer-Seed Bugs in my Home?

Insecticide sprays on the outside of the house are costly and rarely effective, and useless indoors.

Keep them outside

Consult the US Department of Energy Guideline for Durable Attics for more information.

Guide to Durable Attics (pdf)

Intact screens can keep out a variety of fall-invading insects.Reduce indoor invaders by replacing damaged or old screens; sealing gaps around doors and door frames, window frames; and using appropriate screening or mesh on soffits, chimneys and vents, including roof ridge vents. Consult the US Department of Energy Guideline for Durable Attics for more information. Seal gaps at the roof edge, along fascia and wherever utilities like cable wires enter the structure. Inside, seal gaps around light fixtures leading into attic spaces.

When they're inside already

Using a vacuum to collect a large group is effective, but they will leave an odor inside the vacuum cleaner. Collect them by hand in containers (knock them into soapy water) and dispose of them.