Cluster Fly Control in Clintonville, WI

Because of what surrounds the town rather than anything about the houses. Cluster fly larvae parasitise earthworms in the soil, so the population is produced by lawn, pasture and field — and Clintonville is a small village with farmland starting almost immediately past the last street. Properties on the edge of town and along the Pigeon River corridor get the heaviest pressure, but even downtown homes with mature lawns produce plenty locally. It has nothing to do with how clean the house is.

Late August into the first half of September, before the flies start massing on the walls. Once they are into the soffits and wall voids the opportunity has passed for that year and everything after is cleanup. We schedule Clintonville properties early in the season precisely because we are in town — a same-day window is easy to find here in a way it is not for the outlying towns.

South and west, almost always, because they are following the afternoon sun on the warm siding. On the older two-story homes around downtown that usually means the upper wall and the soffit line, which is also where the gaps are. If you want to know whether you have a problem building, stand on the south side of the house on a warm afternoon in late September and look up.

Yes, unless the entry points are sealed, and often even then at reduced numbers — because the flies re-invade from the surrounding land every autumn regardless of what you do to the building. That is why most Clintonville properties do best on an annual early-fall exterior rather than a one-off. Sealing cuts how many get in; the annual treatment cuts how many are on the wall in the first place.

Those are the flies that got into the walls last September and have been dormant there since. A warm winter day heats the void, they wake, and they move toward the light — which is your upstairs windows. It is not a new infestation and there is nothing to treat indoors; vacuum them up. The fix is next September's exterior, not a midwinter spray.

Cluster flies are noticeably larger, darker and slower than house flies, with golden hairs on the thorax, and they move sluggishly rather than darting. If they are massing on the outside walls in autumn and turning up at upstairs windows on warm days, that is cluster flies. Boxelder bugs and Asian lady beetles do the same thing on the same walls at the same time — all three are treated together on the same visit, which is how we handle it here.

Both, and the century-old homes around Main Street are some of the hardest buildings in town for this. Original wood windows, deep soffits, balloon framing and decades of small gaps give cluster flies far more ways in than a modern build. Farm properties on the edge of town get bigger numbers off the surrounding land; the old village homes get more of what arrives actually getting inside. Different problems, same September timing.