Stop Cluster Flies Clustering 

Cluster flies that have plagued many rural homes and farms over recent years are a very seasonal pest. Although it is not yet cool enough yet to induce flies to begin clustering (usually March/April) now is when the last life cycle is beginning to emerge. Therefore now is the time to treat the cluster flies at source; in the lawns and pastures where the eggs, larvae and pupae are.

How to identify cluster flies

Cluster flies are dull black/grey as below. Although not clear on this dead fly the eyes are a deep red-brown.

Cluster flies are slow-moving.

It is their habit of clustering together in dark places such as roof voids and nooks and crannies around a building that gives them their name.

The life cycle of cluster flies

• Eggs are laid in turf through spring/summer
• Larvae that hatch from eggs find and parasitise earthworms
• Larvae pupate in the soil and emerge as adult flies
• Summer – flies mate and lay eggs in the soil
• Autumn – flies cluster in buildings to survive winter

Cluster flies pass through several life cycles during summer but the final life-cycle produces the adults that attempt to overwinter in clusters.

When cool weather first strikes the flies seek shelter in dark and dry corners of buildings. When they find a ‘good’ place to hide for the winter the pheromone (smell) that each fly releases attracts other cluster flies. As more flies join the cluster the pheromone strength builds until all the flies in the area are clustered together in the same place. A home or other building can be infested with many thousands of these slow-moving smelly flies.

Although cluster flies do not pose a human health hazard their huge numbers can be a considerable nuisance, plus, in large numbers, the rancid fat like the smell they produce can be very unpleasant to those whose homes are infested.

Control of cluster flies

Treat your lawns, particularly those close to buildings, with Kiwicare NO Ants Ant Sand or LawnPro Protect. Sprinkle the granules over grass areas and water well in to take the insecticide deep into the soil where it will control the flies before they emerge as adults.

Although some preventative work can be done on homes to stop cluster flies choosing the house as a place to cluster, and clusters can be removed, it is preferable to be pro-active and stop their breeding cycle now.

More on cluster flies and how to control them, before they cluster and after they have clustered and are infesting a building.