Often confused with the bothersome stink bug, the western conifer seed bug is a common fall-time pest. These sap-sucking seed-boring bugs love to inhabit homes, often resulting in full infestations as the temperature cools down. While these insects are harmless, they can become an annoying nuisance when invading homes in large numbers.

In this article, we’ll look at the western conifer seed bug, explain where it gets its peculiar name, and how to best keep them out of your home come autumn.

What Are Western Conifer Seed Bugs?

The western conifer seed bug (WCSB), or by its scientific name Leptoglossus occidentalis, is a true bug (Hemiptera) of the family Coreidae (leaf-footed bugs). This insect gets its name from its preferred food and nesting location, large seeds of conifer trees (pine cones). They have long, flat, shield-shaped bodies, with colors ranging from shades of reddish brown to gray. They possess long antennae, thin spindle-like legs, and wing covers with a zigzag pattern.

These bugs are found across Europe and North America. Overseas they are most commonly in England and Wales. In the U.S., they’re often seen in Northeastern states, specifically New York, Pennsylvania, and Ohio.

Are Western Conifer Seed Bugs Dangerous?

seed bug crawling on board
Image Source: Canva

Western conifer seed bugs are harmless, as they don’t bite, carry diseases, and pose no threat to your home or garden. They’re overwintering insects, meaning they look for a place to hide and stay warm during cold weather. They don’t nest or reproduce in homes, making infestations less likely. However, these bugs are considered nuisance pests due to their:

  • Pervasiveness: Even though these bugs won’t reproduce in homes, houses can be swarmed en masse come fall – this is especially true for homes on the edges of forests.
  • Loud buzzing flight: Their wings are strong and make a loud buzzing hum, similar to that of bees, when in flight.
  • Stench: Like the stink bug, the WCSB produces a foul-smelling liquid when threatened or smashed.

Beyond the home, these bugs are a larger threat to logging industries. The WCSB feeds on the sap of seeds using small, pierce-sucking mouthparts. In the early stages of life, WCSB nymphs drain young, developing seeds, making them a minor threat to seeding gardens. As adults, they begin to target larger, more developed seeds like pine cones, with a preference for the Douglas fir and other conifer species. Due to their food preference, they’re a significant economic pest that damages the viability of conifer tree seed crops. 

Why Are There Western Conifer Seed Bugs in My House?

Like many common pest insects, western conifer seed bugs seek warm places to ride out winter. Unfortunately, your house is a five-star hotel for them, as it offers warmth and shelter. These bugs typically find their way inside through siding, walls, holes in window or door screens, and foundation cracks. One or two inside your home throughout fall isn’t uncommon, but homes near forests can experience dozens of them. Houses with pine trees as a part of their landscaping can also expect to see more of these pests come autumn.

Western Conifer Seed Bugs vs. Stink Bugs and Assassin Bugs

The western conifer seed bug is often confused with several other harmful insect species, namely assassin bugs and stink bugs. These western conifer seed bug look-alikes are more dangerous and troublesome pests, leading to misconceptions regarding the western conifer seed bug. Differences Between Assassin Bugs and Western Conifer Seed Bugs

Differences Between Assassin Bugs and Western Conifer Seed Bugs

seed bug vs. assassin bug graphic
Image Source: Sam Wasson / Today’s Homeowner Team

Confusion regarding assassin bugs comes from their similar appearance, as assassin bugs (also known as wheel bugs or kissing bugs) have a similar body shape, head shape, coloration, and striped abdomen. Unlike western conifer seed bugs, assassin bugs feed on blood, possess a painful bite, and are a vector for Chagas disease. You can tell the difference between the two by looking at their legs, body shape, and markings. The western conifer seed bug has longer hind legs with flat leaf-like spines. Western conifer seed bugs are browner in color, with white zigzags on their backs, whereas assassin bugs are red and black, with no distinct wing cover patterns.

Differences Between Stink Bugs and Western Conifer Seed Bugs

seed bug vs. stink bug graphic
Image Source: Sam Wasson / Today’s Homeowner Team

Another pest commonly confused with the western conifer seed bug is the brown marmorated stink bug (BMSB). Like assassin bugs, stink bugs share many visible features with western conifer seed bugs. They both have similar color patterns, stripes along the sides of their bodies, striped antennae, and shield-shaped bodies. The BMSB is a serious agricultural pest, ruining various fruits, vegetables, and other crops. These smelly home invaders also destroy ornamental plants, making them a plague for homes with gardens or vibrant landscaping plants. Stink bugs share similar habits and defense mechanisms with western conifer seed bugs, furthering misidentifications. Stink bugs overwinter in human habitations, swarming homes in large numbers in fall, and, like western conifer seed bugs, release a foul odor when agitated.

The main differences between stink bugs and western conifer seed bugs are their body lengths, leg shapes, head shapes, and antennae. Stink bugs are shorter and wider than western conifer seed bugs, with a more pronounced shield shape. The head of the western conifer seed bug is longer and thinner than the stink bug’s, and the legs of the stink bug lack the western conifer seed bug’s distinctive leaf-like spines. While both insects have striped antennae, the stink bug’s stripes are yellow and brighter than the western conifer seed bug’s.

How To Prevent Western Conifer Seed Bugs

homeowner caulking window frame
Image Source: Canva

Keeping western conifer seed bugs out of your house comes down to proper home maintenance. Various pests, like western conifer seed bugs, stink bugs, boxelder bugs, and lady beetles, get inside through entry points on the home’s exterior. To best keep insects from invading, you should conduct a yearly home inspection and undertake regular repair work. We recommend doing this inspection during late summer, as temperatures are cooling off, but before insects begin looking to head indoors in early fall. You should go over all parts of your home’s exterior, paying special attention to the following areas:

  • Foundation: Many common fall pests can get into the home through cracks and crevices in the foundation; anything larger than a quarter of an inch should be sealed and filled with silicone caulk or epoxy sealant.
  • Door and window frames: Small gaps in doors and window frames and old and worn-down weather stripping make easy access points for pests. Seal these gaps and replace weather stripping to keep pests outside.
  • Siding: Gaps in siding can lead to numerous pest problems besides western conifer seed bugs and should be repaired promptly. You can repair small siding gaps by using caulk or replacing the entire section. We recommend calling a professional for large gaps where multiple pieces of siding are damaged.
  • Soffits: These are the exterior layers of wood, metal, or vinyl that protect the underside of a roof overhang. Over time soffits can come loose slightly and have small gaps that expose the fascia beneath. Insects can infiltrate these gaps, making them a must on a yearly repair and inspection checklist. While you can repair gaps in soffits and fascia yourself, doing so can be difficult and dangerous. We recommend calling a professional repair or pest control company that handles soffit and fascia repairs.
  • Attic windows and vents: An attic is a prime location for pest incursions. Pests can sneak in through gaps in attic windows or unscreened attic vents. We recommend installing mesh screens on these vents and filling window gaps with caulking.

One thing to remember when trying to prevent western conifer seed bugs is that insecticides and pesticides are not known to work on them. Most leaf-footed bugs are highly resistant to pesticides, which is why many homeowners still report seeing them after thorough spraying.

How To Get Rid of Western Conifer Seed Bugs

Like stink bugs, smashing western conifer seed bugs is not recommended, nor is vacuuming them up, as they’ll release a foul smell. Instead, it’s best to capture and toss them back outside or knock them into a small bowl of water and dish soap.

Final Thoughts

Western conifer seed bugs don’t bite or cause damage to your home, but they’re an unpleasant nuisance since they invade your space and exude an odorous smell. They can also cause damage to your garden by destroying seedlings and are an economic pest that wreaks havoc on the pine tree industry. Ultimately, these pests are not a massive problem if you keep up with your yearly maintenance. But if you live in a heavily wooded area, you may wind up facing a small swarm of them come autumn, so we recommend calling a pest management company.

Editorial Contributors
Sam Wasson

Sam Wasson

Staff Writer

Sam Wasson graduated from the University of Utah with a degree in Film and Media Arts with an Emphasis in Entertainment Arts and Engineering. Sam brings over four years of content writing and media production experience to the Today’s Homeowner content team. He specializes in the pest control, landscaping, and moving categories. Sam aims to answer homeowners’ difficult questions by providing well-researched, accurate, transparent, and entertaining content to Today’s Homeowner readers.

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Lora Novak

Senior Editor

Lora Novak meticulously proofreads and edits all commercial content for Today’s Homeowner to guarantee that it contains the most up-to-date information. Lora brings over 12 years of writing, editing, and digital marketing expertise. She’s worked on thousands of articles related to heating, air conditioning, ventilation, roofing, plumbing, lawn/garden, pest control, insurance, and other general homeownership topics.

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