How To Get Rid Of Cluster Flies: Prevention And Control Tips

June 1, 2026

Have you suddenly noticed large, sluggish flies gathering around your windows during the cooler months?

You’re probably dealing with cluster flies, a common pest that can invade Wisconsin homes, apartment buildings, offices, and commercial properties by the dozens or even hundreds.

The frustrating part? By the time you see cluster flies inside your property, they’ve often already been hiding in your walls, attic, or other secluded areas for weeks or even months. If you want to know how to get rid of cluster flies, the trick is to know what attracts them and take action before they move in.

In this guide, you will learn how cluster flies get in, why infestations occur and the best prevention and control methods to protect your family, tenants, customers and property.

What Are Cluster Flies?

Cluster flies are often confused with common house flies, but there are a number of key differences. Unlike house flies that breed in garbage and food waste, cluster flies spend most of their lives outdoors. As temperatures begin to cool, they look for protected places to spend the winter.

Common hiding places includes:

  • Attics
  • Wall voids
  • Crawl spaces
  • Garages
  • Storage rooms
  • Commercial building ceilings

Once inside, they remain hidden until warmer temperatures cause them to emerge and gather around windows and light sources.

What Attracts Cluster Flies?

Cluster flies aren’t usually attracted to food the way house flies are. But there’s something to be learned from the visual of a house fly dining on dried fruit on a wooden woven tray: exposed food sources can be attractive to a variety of fly species and can add to pest activity around homes and business establishments.

Warm Shelter

The biggest draws for cluster flies, with warm shelter.

As the weather cools, cluster flies look for protected indoor locations in which to hunker down for the winter. As temperatures begin to drop, cluster flies seek out warm, protected spaces where they can spend the winter undisturbed.

Small Gaps And Entry Points

Cluster flies can enter through surprisingly small openings around windows, doors, siding, vents, and other areas of a building’s exterior. Even tiny cracks can provide easy access indoors. Cluster flies tend to gather on south- and west-facing walls because these surfaces retain heat during the cooler months.

The Biggest Mistake Property Owners Make

One of the most common mistakes people make is waiting until they see flies inside the home or building to act.

By that point:

  • The flies have already entered.
  • They may be hiding inside wall voids.
  • The infestation is often much larger than it appears.

The most effective strategy is prevention before cluster flies begin searching for winter shelter.

How To Get Rid Of Cluster Flies

  1. Seal Possible Entry Points
  2. Eliminate Noticeable Flies Safely
  3. Checked Attics and Covered Spaces
  4. Increase Your Home’s Exterior Defenses
  5. Consider Professional Pest Control Services

In situations where cluster fly infestations are recurring or difficult to eradicate, professional pest control services can offer a more comprehensive solution.

Why Professional Pest Control Matters

A trained technician can find hidden entry points, apply targeted preventative treatments, monitor seasonal activity, and create a customized exclusion plan to minimize the likelihood of future infestations.

DIY solutions might eliminate the visible flies, but they seldom eliminate the root cause of the problem. Seasonal cluster fly activity, typical entry points, prevention timing and long-term control strategies. This means more peace of mind for homeowners and less inconvenience for property managers and commercial property owners.

Protect Your Family And Property Before Cluster Flies Invade

Timing is crucial when it comes to how to get rid of cluster flies. The best approach is to prevent cluster flies from entering your home or building. By the time you start seeing flies indoors, the infestation has usually already taken hold. Whether you own a home, manage rental properties or operate a commercial facility, proactive prevention and professional pest management can help keep cluster flies out year after year.

Our trusted professional pest technicians can identify vulnerabilities, stop infestations before they grow, and help protect your family, tenants, customers, and property.

Get your Instant Quote today and take the first step toward a pest-free property.

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