Cluster Fly Control
Cluster flies are a common rural pest, particularly problematic during autumn when they gather in substantial numbers. These flies are often seen clustering around windows, drawn to light during the day, but they eventually seek shelter and hibernate in roof spaces at night. This behavior suggests that if you observe a few cluster flies, there are likely many more hidden within your home, indicating a potential fly infestation. During autumn, cluster flies tend to congregate in large numbers on sun-warmed, south-east facing walls or roof tiles during the day. As evening temperatures drop, they crawl into crevices or under eaves and fascia boards into roof spaces, frequently settling in lofts or wall voids—areas that provide quiet and undisturbed conditions for hibernation over winter.
The common cluster fly is a sizable insect, comparable to a house fly, and can easily be mistaken for one. In the UK, several cluster fly species are recognized, differing in size and coloration; the primary distinction from the common cluster fly lies in the yellowish-golden hairs on its thorax and a striking dark and light chequered abdomen pattern. Common cluster flies exhibit sluggish flight, often resting with overlapping wings. As the name implies, this is the species you’re most likely to find in your attic space.
When spring arrives, cluster flies become active again. However, due to the climate-controlled nature of our homes, they may emerge earlier, mistakenly believing that spring has arrived. By late summer, adult flies depart to lay their eggs in decaying leaves, compost, refuse, and soil. The larvae of cluster flies are parasitic on earthworms, eventually pupating in the soil before emerging as adults to seek shelter for the winter.
Although cluster flies do not bite, they can be a significant nuisance due to the large volumes in which they invade properties for hibernation during winter. You likely wouldn’t want to share your living space with swarms of flies, and for businesses, a fly infestation can be detrimental to attracting customers.
These cluster flies may leave behind tiny dark spots of excrement on walls or windows, which can appear unsightly and are challenging to remove. Another issue arises when dead flies accumulate in wall voids or false ceilings, as they can attract additional pests like larder beetles.
To combat a cluster fly infestation, it's essential to understand that these insects can enter your home through the smallest of cracks around door and window frames or any tiny openings. To limit access, you can fill cracks and crevices in walls, window, or door frames with caulking. However, it’s unlikely to prevent all cluster flies from getting into your loft. DIY fly sprays can be effective when applied directly to the flies but may not affect those already hibernating. In cases of large infestations, professional pest control treatments are often necessary.
Wilde Pest Control offers expert treatment options for cluster flies, which include the use of insecticides with a strong residual effect to target flies as they emerge from hibernation. Ultra Low Volume (ULV) treatments or smoke generators can access hard-to-reach areas where cluster flies hide, providing rapid and effective knockdown. It's crucial to note that infestations can recur within the same season, particularly if treated too early in the autumn. This recurrence is due to pheromones left behind by cluster flies already in the building, which attract new flies to the site. Therefore, a second treatment in the spring, just before the flies leave the building to lay their eggs, can be beneficial.