Fall Pest Invasion Alert: Stink Bugs, Cluster Flies & Asian Lady Beetles in New Hampshire

Fall pest season starts before you see them inside—by then, they're already in your walls.

Every fall, thousands of New Hampshire homeowners face the same frustrating problem: their homes become targets for swarms of insects looking for a warm place to spend the winter. If you've noticed shield-shaped brown bugs clustering on the sunny side of your house, slow-moving flies gathering in your attic, or what looks like a ladybug invasion on your windows, you're dealing with New Hampshire's most common fall invaders—brown marmorated stink bugs, cluster flies, and Asian lady beetles.

These pests aren't just annoying. They can stain your walls, create foul odors, and make your home feel like it's under siege from September through November. The good news? With the right prevention strategies—especially natural methods that protect your family and pets—you can keep these unwanted guests outside where they belong.

Why Fall Pests Target New Hampshire Homes

Your home's warm walls are the perfect winter hideout for stink bugs, cluster flies, and lady beetles.

New Hampshire's dramatic temperature swings trigger a survival instinct in these insects called diapause—essentially a hibernation state that allows them to survive our brutal winters. As nights drop into the 40s and 50s in late August and September, stink bugs, cluster flies, and Asian lady beetles start searching for protected spaces to overwinter.

Your home is the perfect target. These pests are drawn to structures that absorb heat during the day, which is why you'll often see them congregating on south and west-facing walls during sunny autumn afternoons. They're not trying to live in your house—they're trying to hide in your wall voids, attic spaces, and any gap they can squeeze through until spring arrives.

The timing matters more than most people realize. By the time you're seeing bugs inside your home, they've already found entry points and established themselves in your walls. That's why prevention needs to happen in late summer, before the invasion begins.

Brown Marmorated Stink Bugs: New Hampshire's Most Notorious Fall Invader

The brown marmorated stink bug wasn't even in New Hampshire until the early 2000s. Originally from Asia, this invasive species was first detected in the Seacoast region around Portsmouth and has since spread throughout the state. Now it's one of the most complained-about pests our customers call about every fall.

How to identify stink bugs: These shield-shaped insects are about the size of a dime, with a mottled brown and gray pattern on their backs. Look for the distinctive white bands on their antennae and the alternating light and dark pattern along the edges of their abdomen. When disturbed or crushed, they release a pungent odor that many describe as similar to cilantro or coriander—hence the name.

Brown marmorated stink bug—about the size of a dime with distinctive white bands on its antennae.

Where they hide: Stink bugs seek out cracks around windows and doors, gaps in siding, tears in window screens, and openings around utility penetrations. Once inside your walls, they can remain dormant for months. On warm winter days, they sometimes emerge inside your home, confused by indoor heating into thinking spring has arrived.

The damage they cause: While stink bugs don't bite, sting, or cause structural damage, they're a serious nuisance. Their defensive odor can permeate rooms and is difficult to eliminate from fabrics. They can also leave brown staining on curtains, walls, and light-colored surfaces. For New Hampshire's agricultural community, they're an even bigger problem—stink bugs cause significant damage to apple orchards, vegetable gardens, and ornamental plants.

Cluster Flies: The Attic Invaders

Cluster flies are one of the most misunderstood pests in New Hampshire. Many homeowners assume they have a sanitation problem when these large, sluggish flies appear in their homes, but cluster flies have nothing to do with garbage or filth.

The surprising truth about cluster flies: These flies spend their larval stage as parasites of earthworms in your lawn. That's right—the same earthworms that benefit your soil are hosts to cluster fly larvae. When the flies emerge as adults in late summer, they seek out structures to overwinter in, often returning to the same buildings year after year.

How to identify cluster flies: Cluster flies are larger than common house flies, with a distinctive golden or yellowish fuzzy patch on their thorax. They move slowly and sluggishly, especially on cold days. Their name comes from their habit of clustering together in large groups, often in attics, wall voids, and around windows.

Cluster flies are larger than house flies with golden fuzzy hairs on their thorax.

Why they're particularly problematic in New Hampshire: Our older housing stock, with its many gaps and crevices, provides perfect entry points for cluster flies. Historic homes, farmhouses, and rural properties are especially vulnerable. Once cluster flies establish a home as their overwintering site, they release pheromones that attract more flies to the same location—meaning infestations tend to worsen year after year if left unaddressed.

The deadline for prevention: According to University of New Hampshire Extension entomologists, cluster fly exclusion work needs to be completed before September 10th to be effective. After this date, the flies have already begun entering wall voids and attic spaces.

Asian Lady Beetles: Not Your Friendly Garden Ladybug

Those orange and red beetles swarming your windows every October aren't the beneficial ladybugs you remember from childhood. Asian lady beetles (sometimes called Halloween beetles due to their timing) are an invasive species that, while they do eat aphids, have become a significant household pest in New Hampshire.

How to tell Asian lady beetles from native ladybugs: Asian lady beetles are typically larger than native species and can range from pale orange to deep red. The key identifier is the black M-shaped or W-shaped marking on the white area behind their head. Native ladybugs lack this distinctive marking. Asian lady beetles also tend to have more variable spot patterns—some have many spots, others have few or none.

The black M-shaped marking behind the head identifies Asian lady beetles from native ladybugs.

Why they're worse than regular ladybugs: Unlike native ladybugs, Asian lady beetles aggregate in enormous numbers on buildings and actively seek to enter homes. They can bite (though it's more of a pinch), and they release a foul-smelling yellow fluid when disturbed that can stain surfaces and trigger allergic reactions in sensitive individuals. Some people develop allergic rhinitis or even asthma symptoms from heavy Asian lady beetle infestations.

Peak invasion timing: Asian lady beetles typically swarm on warm, sunny days in October and November, especially after the first hard frost. They're particularly attracted to light-colored buildings and homes near wooded areas or agricultural fields.

Natural Prevention Methods That Actually Work

At Purely Nature's Way, we believe in addressing pest problems with the least toxic methods first. Here are proven natural strategies for preventing fall pest invasions in your New Hampshire home.

Seal Entry Points Before September

The single most effective prevention method is physical exclusion—sealing the gaps and cracks that pests use to enter your home. This work should be done in August before pests begin seeking shelter.

Focus on these common entry points:

Windows and doors are the primary entry points for fall invaders. Check weatherstripping on all exterior doors and replace any that's worn or damaged. Inspect window frames for gaps between the frame and siding, and caulk any openings. Repair or replace torn window screens—even small holes are large enough for stink bugs and lady beetles to squeeze through.

Utility penetrations where pipes, wires, cables, and vents enter your home are often overlooked. Use expanding foam or caulk to seal gaps around dryer vents, air conditioning lines, cable entry points, and plumbing penetrations. Pay special attention to where utilities enter through your foundation.

Sealing gaps around windows in August is your best defense against fall invaders.

Soffits and roof lines provide easy access for all three fall invaders. Inspect soffit vents and ensure screening is intact. Check where the roof meets the siding for gaps, and examine the flashing around chimneys and roof penetrations.

Foundation cracks and gaps allow pests to enter at ground level and work their way up into wall voids. Walk your home's perimeter and note any cracks in the foundation, gaps where siding meets the foundation, and openings around basement windows.

Essential Oil Deterrents

Natural prevention tools: peppermint oil, diatomaceous earth, caulk, and weatherstripping.

While no essential oil will completely repel fall pests, certain scents can make your home less attractive to them. These work best as part of a comprehensive prevention strategy, not as a standalone solution.

Peppermint oil has shown some effectiveness at deterring stink bugs. Mix 10-15 drops of pure peppermint essential oil with two cups of water in a spray bottle and apply to window frames, door frames, and other entry points. Reapply every few days during peak invasion season.

Neem oil has natural insecticidal properties and can be applied to exterior surfaces where pests congregate. Mix according to package directions and spray on sunny-side walls, around windows, and near entry points.

Clove and lemongrass oils may help deter Asian lady beetles. A mixture of these oils diluted in water can be sprayed around windows and doors.

Important note: Essential oils need frequent reapplication, especially after rain. They're best used as a supplement to physical exclusion, not a replacement.

Diatomaceous Earth for Barrier Protection

Food-grade diatomaceous earth (DE) is a natural powder made from fossilized algae that damages insects' exoskeletons, causing them to dehydrate. It's non-toxic to humans and pets but effective against crawling insects.

Apply a thin line of DE around your foundation exterior, in attic spaces along the edges where roof meets walls, around window frames in attics and crawl spaces, and in wall voids if you have access. DE loses effectiveness when wet, so focus on protected areas and reapply after rain.

Reduce Exterior Attractants

Make your home less appealing to fall invaders by modifying the conditions that attract them.

Exterior lighting draws insects to your home at night. Switch to yellow or amber bulbs, which are less attractive to insects. Consider motion-activated lights instead of lights that stay on all night. Move decorative lighting away from doors and windows.

Vegetation management helps reduce pest pressure. Trim shrubs and trees so they don't touch your home's exterior. Keep mulch at least 12 inches away from your foundation. Remove leaf litter and debris from around your foundation in fall.

Moisture control is critical because all three fall invaders are attracted to moisture. Fix leaky gutters and downspouts, ensure proper drainage away from your foundation, and address any moisture issues in basements or crawl spaces.

Safe Removal Without the Smell or Stains

Despite your best prevention efforts, some pests will inevitably make it inside. Here's how to remove them without triggering defensive odors or staining.

The vacuum method is the safest way to remove fall pests. Use a shop vac or a vacuum with a bag you can dispose of immediately. Vacuum pests directly without crushing them. For stink bugs specifically, some people place a knee-high stocking inside the vacuum hose, secured with a rubber band—the bugs get trapped in the stocking, which you can then tie off and dispose of without the smell permeating your vacuum.

Vacuum stink bugs instead of crushing them to avoid releasing their defensive odor.

The soapy water trap works well for stink bugs and Asian lady beetles. Fill a wide-mouth jar or bucket with soapy water and use a piece of cardboard to gently brush or knock the pests into the water. They'll drown quickly without releasing their defensive chemicals.

The light trap technique takes advantage of these pests' attraction to light. In a dark room where pests are present, set up a desk lamp over a pan of soapy water. The bugs will fly toward the light and fall into the water.

What NOT to do: Never crush stink bugs or Asian lady beetles inside your home—this releases their defensive odors and can cause staining. Avoid using bug spray indoors on these pests, as it often causes them to release their chemicals before dying. Don't sweep them up with a broom, which tends to crush some while scattering others.

When Natural Methods Aren't Enough

Sometimes, despite your best efforts, fall pest pressure is simply too high for natural methods alone—especially in rural properties surrounded by agriculture, homes with extensive entry points, or buildings with established multi-year infestations.

That's when professional intervention makes sense. A targeted exterior barrier treatment applied before fall invasion season can dramatically reduce the number of pests that make it inside. These treatments focus on the areas where pests congregate—sunny-side walls, around windows and doors, soffits and eaves—creating a protective barrier that pests must cross to enter.

At Purely Nature's Way, we take a natural-first approach even with professional treatments. We start with comprehensive exclusion work, identifying and sealing entry points. We use the least toxic effective products, targeting them precisely where they'll have the most impact while minimizing exposure to your family and pets.

For severe infestations or homes with extensive entry points, we recommend scheduling a pre-season inspection in August. This gives us time to complete exclusion work before the September invasion begins and apply preventive treatments when they'll be most effective.

The New Hampshire Homeowner's Fall Pest Prevention Checklist

August (Before Labor Day):

• Walk your home's exterior and note all gaps, cracks, and potential entry points

• Repair or replace damaged window screens

• Check and replace weatherstripping on exterior doors

• Caulk gaps around windows, especially on south and west-facing walls

• Seal utility penetrations with expanding foam or caulk

• Schedule professional exclusion work if needed

Early September:

• Apply diatomaceous earth to attic edges, crawl spaces, and foundation perimeter

• Begin essential oil applications to entry points

• Switch exterior lighting to yellow/amber bulbs

• Trim vegetation away from home's exterior

• Clear leaf litter and debris from foundation areas

Mid-September through October:

• Monitor south and west-facing walls for pest activity

• Vacuum any pests found inside promptly

• Reapply essential oil deterrents weekly

• Keep doors and windows closed during warm afternoon hours when pests are most active

Late October through November:

• Continue indoor removal with vacuum or soapy water methods

• Note which areas had the heaviest pest pressure for next year's prevention planning

• Schedule a post-season consultation to plan improvements for next fall

Your month-by-month guide to keeping fall pests out of your NH home.

Protect Your New Hampshire Home This Fall

Fall pest invasions are frustrating, but they're not inevitable. With proper preparation—starting in August, before pests begin seeking shelter—you can dramatically reduce the number of stink bugs, cluster flies, and Asian lady beetles that make it inside your home.

The key is acting early. By the time you're seeing pests inside your house, they've already found entry points and established themselves in your walls. Prevention is always more effective than removal.

If you're dealing with a current infestation or want professional help preparing for next fall's invasion, Purely Nature's Way offers comprehensive fall pest prevention services throughout New Hampshire. Our natural-first approach means effective pest control without unnecessary chemical exposure for your family and pets.

Ready to take back your home from fall invaders? Contact Purely Nature's Way today for a free fall pest prevention inspection. Call [PHONE] or request your inspection online.

Frequently Asked Questions

Do stink bugs bite?

No, brown marmorated stink bugs do not bite humans or pets. They have piercing mouthparts designed for feeding on plants, not animals. Their only defense mechanism is the foul-smelling chemical they release when threatened.

Why do I have cluster flies but no garbage or filth in my home?

Cluster flies have nothing to do with sanitation. Their larvae are parasites of earthworms, so they develop in soil, not garbage. Adult cluster flies enter homes purely to find a protected place to overwinter—your home's cleanliness doesn't attract or repel them.

Are Asian lady beetles dangerous?

Asian lady beetles can bite (it's more of a pinch), and their defensive secretions can trigger allergic reactions in some people, including skin irritation, respiratory symptoms, and eye irritation. While not dangerous for most people, those with allergies or asthma should avoid handling them.

Will the pests in my walls damage my home?

Stink bugs, cluster flies, and Asian lady beetles don't eat wood, fabric, or stored food. They don't reproduce inside your home. The main concerns are nuisance, odors, and staining from defensive secretions.

Why do pests keep coming back to the same house every year?

These insects release aggregation pheromones that attract others of their species to successful overwintering sites. Once your home has been "marked," it becomes increasingly attractive to future generations. Breaking this cycle requires comprehensive exclusion to prevent entry.

When is it too late to prevent fall pest invasions?

For cluster flies, exclusion work should be completed before September 10th. For stink bugs and Asian lady beetles, you have a bit more time—late September exclusion can still be effective. However, the earlier you start, the better your results will be.

Can I use pesticides to kill pests inside my walls?

This is generally not recommended. Dead insects inside wall voids can attract secondary pests like carpet beetles and create odor problems. It's better to prevent entry and remove live pests that make it inside.

Purely Nature's Way provides natural-first pest management services throughout New Hampshire, including Littleton, the White Mountains, Lakes Region, and surrounding communities. Our approach prioritizes prevention, exclusion, and the least toxic effective methods to protect your home and family.