Return of the Cluster Flies
7th March 2011
The annual influx of cluster flies into New Zealand rural homes and farms has begun in earnest. Rural supplies stores
and hardware stores around the country are reporting a sudden and dramatic increase in customers seeking help and advice
on how to get rid of these flies.
This year it is likely that more homes than ever will be infested by cluster flies. The numbers have been increasing and
the problem spreading for the past decade. Also the warm moist La Nina weather through the summer months provided ideal
conditions for the flies and the earthworms on which the fly larvae feed.
In autumn, cluster flies gather together in dark dry nooks and crannies in homes and other buildings. They congregate
in order to survive through the winter in a dormant state. The clusters of flies are often found in attics, ceiling
spaces, gaps around ill fitting windows and corners of rooms. The cold snap sweeping the country is signalling to the
flies that it is time to get together and find shelter. On warm days the clusters will become active and flies are found
emerging from their hiding places, sometimes in their thousands. The dull black flies have a sweet sickly smell and tend
to be slow moving in their semi active state.
The good news for those affected by cluster flies is that there are ways to reduce the risk of being pestered by the
flies and of getting rid of them if they are already formed clusters.
David Brittain of pest control manufacturer Kiwicare advises sealing up any places around the home where the flies could
crawl in, such as gaps around eaves or ill fitting door and window frames. If all entry points cannot be sealed then the
use of long lasting surface spray insecticide on the entry points and warm north facing walls will help control the
flies before they have a chance to move in.
Kiwicare have launched a new product that is effective against cluster flies. The new NO Flies Bait can be placed around
the exterior of buildings. The flies are attracted to the bait and are killed when they feed on it. David says "Place
the bait several meters from the house to attract the flies away from the building and to kill them before they can move
in. It is also not too late to reduce fly numbers by using soil insecticide such as Kiwicare Lawngard Prills on lawns
and pasture from where the flies emerge as adults."
If clusters have already formed, the use of bug bombs or borer fumigators will knock the flies down in hard to reach
spaces. Where possible collect and dispose of the flies as they continue to release the pheromone chemical that attracts
the flies together. Spray surfaces where cluster flies have congregated with long lasting surface insecticide to prevent
new clusters forming in the same place.