overwinter pests crowded together

Now that the fall season is officially here, two things are certain to follow - colder weather and common nuisance overwintering pests...sigh! And we know that snow is coming too, but let’s not jinx ourselves.

It’s a common misconception that all insects and rodents die off in the fall and winter seasons as temperatures transition from cool to cold to freezing, and ice and snow blanket the outdoors. There are in fact, many pests that are actually really good at finding warm, dry places to hide and hibernate and safely wait out winter. This is called ‘overwintering’. While you may see less of these pests in this cooler October weather, they are still around, lingering about, soaking up every minute of sun and heat and preparing to overwinter. 

Pests like cluster flies, Asian lady beetles, boxelder bugs, pine seed bugs, wasps and hornets, and mice are excellent at finding refuge indoors from late fall to early spring. These 7 pests are important to watch out for because they can become a huge pest control issue.

Cluster flies are often the first to overwinter. Cluster flies are those large, slow moving, noisy flies that seem totally confused while they fly and congregate around your windows and light fixtures. From late summer to early fall, cluster flies love to bask in the warm sunshine on walls of homes and businesses. In some cases, they congregate in enormous masses which can be quite alarming. This is very common for those who live in the country. When evening approaches bringing along it’s cooler temperatures, cluster flies seek refuge into homes and businesses through holes, cracks and crevices. Depending on temperatures, they may come out again the next day to enjoy the sun and sneak back inside if the temperature cools again during the day or at night. They will repeat this until they are ready to hibernate, in which they will remain indoors until spring. Once indoors, cluster flies (like most overwintering pests) commonly hide in secluded areas like attics and wall voids and remain inactive until spring.

Wasps & hornets are a nuisance pest around the same time as cluster flies. In late summer to early fall, the queen wasp and queen hornets lay their eggs which will develop into adult male and fertile females. Once they have mated, newly fertilized female wasps & hornets leave the colony to find their own protective shelter to overwinter leaving the rest of the wasp & hornet colonies to die over winter. These fertilized females will become the new queens in the upcoming spring and be responsible for building new colonies.

Next come the overwintering boxelder bugs and pine seed bugs. Like cluster flies, these pests are attracted to the exposed south sides of houses and buildings to bask in the warmth of the late summer and early fall sun. After sunset, pine seed bugs and boxelder bugs will crawl into wall voids and attics through cracks and gaps in the siding, eaves, foundation or around windows. They also remain inactive during the cold, hiding in wall voids and attics. Asian Lady beetles begin overwintering once farm fields are harvested for the season and aphids (what they eat) disappear. They too, will find similar ways into indoors as pineseed bugs, boxelder bugs and cluster flies, and sleep winter away.

Last, and unwanted the most, come the mice. Now, mice can be an issue any time of year, however they can be more problematic in the fall when they are driven away from fields during harvesting. With insufficient shelter, food and water outdoors, they scurry indoors to help guarantee their survival over the winter.

There are 2 things you can do to prevent these overwintering pests from becoming an issue inside your home or business.

The first is to Pest Proof. If you’re able to prevent bugs, insects and rodents from getting inside your home or business, you’ll avoid pest control issues. Check out and try these helpful pest proofing tips we’ve shared in our blog and Pest Library:

The second is to get a Fall Pest Control Treatment. Fall is the perfect time of year to get ahead of and prevent pest issues, because it’s the time of year when overwintering pests want to be indoors, safe and warm, so they can survive the winter and emerge in the spring. Many people believe that finding these pests in their homes in the springtime means that they are experiencing a ‘spring-time’ pest control issue. These pests that have caught you off-guard are really from the fall but did not surface as a pest nightmare until the spring. Sometimes on very mild winter days, where the sun beats down and temperatures rise to spring-like levels, this fall pests awaken by mistake thinking its spring and head for your windows, doors and lights. Combining an annual fall pest control service with a spring pest control service gives the most protection and best results. It prevents these pests from getting indoors now in the fall, when they need the shelter the most, and it will address in the spring any overwintering pests that did make it inside, and will become a nuisance when they wake up ready and want to go back outside.

Why choose Environmental Pest Control this fall (and any other time of the year)? Our business was founded 30+ years ago on our understanding of boxelder bugs, pineseed bugs, Asian lady beetles, cluster flies, mice and wasps and hornets, and how to expertly manage, control and eliminate them. 

Learn more about our rewarding referral program and great special offers, like 50% off our Rodent Control program.

Good luck with your pest proofing and if we can be of any help, do contact us.


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