Insects & Arachnids We Address

  • Ants
  • Mites
  • Wasps
  • Spiders
  • Ear-wigs
  • Roaches
  • Cluster Flies
  • Box Elder Bugs
  • Western Conifer Seed Bugs
  • Multi-colored Asian Lady Beetles
  • Centipedes and Millipedes, etc.


The Cluster Fly

You might first notice the cluster fly as it noisily buzzes at your sunny windows on a warm winter day. This rather sluggish fly will appear dead as it lies, belly up, on your window sill. But, a tiny poke will send it buzzing back into action. In Vermont, the cluster fly (pollenia rudis) is a common inside wintertime pest in those areas where a small earthworm (allobophora rosea) thrives. Hospitals, schools, commercial buildings, and homes are all affected. During the summer months, the larva of the cluster fly burrows into the earthworm and feeds upon it. When ready, the larva leaves its host and pupates in the soil. Soon, an adult cluster fly emerges. Up to four generations can be produced, each summer. When the days shorten and the chill of autumn arrives, the adult fly seeks a hibernation spot. Loose tree bark, plant debris, and stone walls provide natural, outdoor hiding places. And your home provides an additional hibernation place.

The cluster fly resembles a common house fly, yet is larger. The fly enters buildings through tiny crevices: under the siding; around windows; through vents with no screens. Notorious for its invasion of attics, the cluster fly is often referred to as an “attic fly.” It doesn’t breed in your home and it doesn’t pose a health threat. The cluster fly does become a serious nuisance pest when stimulated by the warmth of your heated building. Considering it to be spring, the cluster fly resumes its natural behavior- congregating at the windows or about the lights of occupied rooms. (The flies will exit your home in the spring, when the outdoor temperatures remain warm.)

Control Procedures

A vacuum works fine on the sluggish cluster fly. However, the next warm day will produce another noisy crop, and you’ll need to vacuum again! We, at Vermont Pest Control, can provide an exterior treatment that will prevent the cluster fly from entering your home. Careful carpentry or caulking will exclude larger pests, but since the cluster fly is capable of entering through small and obscure openings we place an insecticidal barrier on key areas of your home. This barrier, when sprayed on your building, acts as a repellent.

Some customers ask about having their grounds treated also. Since the flies are known to travel more than one mile in search of hibernation sites, this is really not a viable option.

We would like to emphasize that this insecticidal treatment is entirely an exterior application. No pesticides will be used inside your living space. Before applying any chemical, all windows, doors, and ventilation openings should be closed. Air conditioners should be turned off. After treatment, you will want to wipe the windows clean, however, great care should be taken to avoid removal of the application.

Treatment Timing

Timing the treatment with the hibernating activity of the cluster fly, which is usually late August to mid-September in this region, is critical. A significant number of flies may enter buildings near the end of the activity period if treatments are applied earlier than August 20th. Some may have already entered if the chemical is applied later than September 15th. Regular seasonal weather patterns prevailing, the recommended period for treatment is August 15th – September 15th.

The insecticidal barrier is effective for many weeks. A single treatment, on most buildings, provides protection until heavy frosts halt outdoor fly activity, in mid-November, or earlier.

FAQs, Tips & Sage Advice

  • Painting Your Building – Please plan to have your home painted or stained several weeks before our treatment, to allow the paint to “cure.” Power-washing your home after our treatment will greatly diminish the efficacy rate.
  • Windows & Screens – Since we apply our product around your windows, we ask you to have the windows closed before our service. You can leave your window screens on or take them off – this is your call. Lighter-colored screens will less show spottiness while dark-colored screens will show more
  • Pets – It is best for your pets to be inside the building or off-site during the fly treatment and, until the product is dry.
  • Vegetable Gardens & Fish Ponds – Should you plant a vegetable garden or build a fish pond/pool close to your home/building, you may want to cover it with a tarp before our service. Or, you could ask us to avoid that area. (However, if the veggie garden or pond is near windows and we avoid treating, there is a great chance of flies entering via this unprotected area.)
  • Day-Before Notice – Due to weather conditions and scheduling parameters, we can only provide a call, THE DAY BEFORE service.
  • Window Washing – Please remember that the cluster fly treatment will spot the windows. Most of our customers arrange for window cleaning to be done after our service – which is perfect timing for clear fall foliage viewing! (Power-washing, or spraying your windows with a hose, may remove our product.)
  • The Color of Your Home – Since the product we use is a wettable powder, it leaves a light-colored spotting when it dries. Most of this spotting will wash off and disappear with repeated exposure to sunshine and rain. Dark-colored homes will show more spotting, so it is YOUR call as to whether this treatment is compatible with your sense of aesthetics.
  • The Tightness Factor – Some homes and buildings are tighter than others. Our treatment will definitely keep overwintering insects under control in a tight building. The rate of control declines when the tightness of a building decreases.

Historically, we have noted a few harder-to-treat buildings. Often, these homes are older and looser or the design renders the building more resistant to the cluster fly treatment. A few examples:

  • Log Homes – particularly older, dark-brown log homes that are situated in an open area and near working farms or fertilized fields.
  • Board & Batten-sided Homes – as these buildings age, the siding often warps, creating voids for flies to enter.
  • The Quintessential Farmhouse – if this building has not been renovated, the flies will easily enter.
  • Glass Homes – not literally made of glass, but homes with many large windows on the southern and western sides of your house are prone to heavy fly activity.

A few homeowners with “difficult fly homes” [as in one of the above categories] have opted for a second seasonal treatment. Other homeowners, who are aware of their building’s limitations, are pleased with the control they do receive, with one treatment.