Friday, October 11, 2019
PEST OF THE MONTH — LESSER HOUSE FLIES
Managing that annoying house fly It is at this time of the year, as the weather warms, that the urban pest season starts to impact on us. Generally, the first thing we notice is the increase in fly numbers. One fly species of considerable annoyance is Fannia canicularis (common name: lesser housefly, or sometimes referred to as the ‘poultry yard fly’). The lesser housefly is considered a cool climate species, particularly more prevalent in spring and autumn. After lying dormant through the winter months and having survived these cooler temperatures, lesser housefly suddenly begins to emerge in numbers. Certain environments contribute to the rapid increase in populations. One example is the presence of chickens or having poultry sheds nearby. They often are an enormous contributor to lesser housefly numbers. The reason for this is lesser house fly prefer to lay their eggs in chicken manure over any other decaying medium. Similarly chicken manure is also a particularly favourable maggot food source. Lesser houseflies have some serious breeding capacity. Eggs are laid in batches, approximately 50 eggs each. Would you believe that one single female fly can lay over 2000 eggs during her lifespan. Furthermore in a warm environment (25 degrees) the lifespan of lesser housefly, beginning from egg to adult, takes only 22 days. Obviously, this means a lesser house fly infestation can very quickly develop into a huge problem. Adult flies tend to congregate in numbers in certain areas. Favourites are shaded areas near poultry yards, within garages, porches and the internal environment of our houses. Interestingly often these represent areas where there is little air movement. One reason the lesser housefly prefers these environments is simply that they are unable to fly in winds that exceed 25 kph. Contrary to belief, lesser houseflies are not really interested in our food so are not often a problem with this aspect. Instead they create a nuisance factor by flying in a circular pattern usually below a hanging light fitting or a light source. This is likely to be located in the middle of a room. Similarly they can be found swarming in
Lesser house flies congregating on a porch wall.
front of us when we are sitting on a sheltered veranda. This annoying flight path of the lesser housefly more often than not is at human face height, thus maximising their nuisance factor. The question is how to control lesser housefly populations. Actually control can be particularly difficult especially when large numbers of flies are continuously emerging from a breeding source that includes a poultry shed or nearby animal manure or compost. Ultimately the best method of control is via removal of this breeding material and the implementation of this regular hygiene practice. Finally, for the average house owner there exists a vast range of fly control devices such as sticky tapes, insect lights, pheromone traps, fly bags and fly sprays that can be used but these may not always significantly reduce fly levels in heavily infested areas. Reducing numbers, in terms of restricting flies entry into houses is the best option, particularly for those houses located near high fly population areas. A long-term, and effective solution will involve the installation of fly excluding screens on windows and doors. ■ Brent Page is a Horowhenua Entomologist and Director of Nature’s Way Pest Control. For more information, visit www.nwpc.co.nz/pests/flies
Reducing numbers, in terms of restricting flies entry into houses is the best option, particularly for those houses located near high fly population areas. A long-term, and effective solution will involve the installation of fly excluding screens on windows and doors.
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