Prepare for the Cluster Fly Invasion

Media Release

Prepare for the Cluster Fly Invasion

24th March 2011

The first signs of the annual invasion of cluster flies into homes, farms and other buildings have been reported to Kiwicare.

As many people will know from previous bad experience the clusters of these flies can be huge; hundreds or thousands of flies in single clusters. The flies do not carry disease but the nuisance is considerable when they move into buildings. The flies produce a sickly sweet smell and on warm autumn days will wake from their dormancy to be found dropping out of light fittings and crawling around the home in large numbers. They have been found lying several centimetres deep on the floor of houses when the homeowners arrived home from a few days away. Each year sees a bigger problem than the year before and this year’s warm moist weather is likely to contribute to the worst year ever.

Cluster flies are members of the blowfly family; they are slow moving, dull, black flies. Their larvae parasitize earthworms in lawns and pasture through the summer months and each year they form the clusters, for which they are named. They seek out dark, dry places, often in homes, farms and other buildings. The clusters start forming in autumn when the flies gather together in order to survive through the cold winter months in a dormant state.

For more than a decade, their numbers appear to have been increasing and consequently they have caused more problems for people in many rural areas of New Zealand. The problem is often blamed on the increase in dairy farming but changes in climate may also be influencing the increase in infestations.

The flies seek out dark dry places such as attics, ceilings, eaves, gaps around windows, doors and between roof tiles. When a fly finds a suitable place to hibernate it emits a pheromone (transmitting chemical) that attracts other cluster flies. As clusters grow, the level of pheromone increases and more flies are attracted.

Kiwicare advises that now is the time to be proactive and prevent the clusters forming in your home. It is much easier to prevent clusters forming than it is to get rid of them when they have begun gathering together. Treat areas where clusters might form and where flies might be able to gain entrance to a building using a long lasting surface insecticide such as Kiwicare’s professional strength NO Bugs Super. Spray entrances to attics around eaves, vents, gaps in weatherboards and roof tiles, around windows and doors and any other entry points. Gaps around opening windows and other spaces can be painted with NO Bugs Super insecticide. Such treatment will kill the flies if they try to enter the voids and prevent the clusters forming.

If clusters have already begun to form, spray the flies directly with the insecticide or use a total release aerosol such as the Kiwicare Bug Bomb in areas which cannot be easily accessed to spray. Be sure to collect and dispose of all dead flies where possible because the flies continue to release their pheromone even after death and will attract more flies. The pheromone may also linger where the clusters formed, so the surfaces where clusters formed should be treated to kill flies that would otherwise collect there.

To control the larvae, lawn areas can be treated with soil insecticide such as Lawngard Prills used for grass grub control. This is best done through summer but may have some benefit in autumn months.

Kiwicare provide further advice on control of cluster flies at www.kiwicare.co.nz

About Kiwicare:

Kiwicare Corporation Limited is a New Zealand owned and operated company offering New Zealand’s most comprehensive range of pest control products. Kiwicare is committed to providing top quality products, advice and service on controlling pests in your home and garden.

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