Controlling house flies with manure traps

ILEIA Newsletter • 13 nº 2 • July 1997

Everybody knows how disturbing a house fly can be and many have suffered illness transmitted by this annoying insect. Much money is spent on controlling it using insecticides, parchments, electrical traps and many other methods, but without sustained effect. On livestock farms in particular, fly populations may grow beyond the limit of tolerance, creating sanitary hazards for both animals and people. In a number of countries, this is a reason for prohibiting livestock near or in urban centres.

CEDEPAS (the Ecumenical Centre for Advancement and Social Action, Huancayo, Peru) was confronted with this situation while implementing livestock development programmes in the densely populated Mantaro valley, including the outskirts of Huancayo, the urban centre and commercial capital of Peru's central highlands. In order to cope with the problem, practical experiments were carried out with fly traps and other ecologically sound methods. But none of these was found to work satisfactorily, until the idea was born to check the fly in its early development stage using the larvae for fodder.

The manure trap

Flies normally lay their eggs in earth or manure. The house-fly is particularly attracted to pig dung. Consequently, all one has to do is to provide an ideal medium for the flies in which they will lay their eggs and then wait until the maggots emerge. Incidentally, during this process the stinking manure is converted into one that smells better, although not as pleasant smelling as compost.

In Huancayo, we constructed wooden crates of 1.5m x 0.75m x 0.20m, using cheap eucalyptus planks, but one can of course vary size and material according to needs and availability of materials. The crate is then filled up to a depth of 15 cm with fresh pig manure. Avoid dung with a lot of straw if harvesting of the pupae is planned. If pig manure is in short supply, other types of dung may be used and covered with pig manure, which is the most effective for attracting flies. If pig manure is unavailable, the next best option is guinea-pig dung, followed by horse manure. Fermented plants and cow dung may also be experimented with, to improve the pleasant smell (pleasant for the flies, of course), although we have no experience in this field.

Next, put the crate in a spot where the flies will have easy access, protected from direct sunlight, rain and wind. The smelly manure will immediately attract the flies and encourage them to deposit their eggs. The first maggots emerge after two days. After a week, the crate is covered by a strong plastic foil or something similar, to accelerate the growth of the maggots. Two weeks later the maggots will start to pupate.

Excellent fodder value

Feeding these pupae to your chickens will show you the unmatched quality of the pupae as a fodder source. If you only have a few chickens, be careful that they do not grow too fat!

Alternatively, you can harvest the pupae, although much more work is then required. Put the manure with the pupae in abundant water and the living pupae will float to the surface. Harvest them and dry them in full sunlight or in a solar drier. This should take some two days. The drying process has to occur rapidly to prevent the flies from emerging. The pupae can then be processed into flour, with a similar smell and texture to fish flour, with the following composition per kilo: humidity 40 g, total proteins 638.4 g, fibre 0.0 g, ash 64.5 g, crude fat 86.0 g and NFE (nitrogen free extract) 171.1 g. With an unbelievably high protein content of 64%, you obtain a high value component for mixing concentrates.

One trap will yield some 150g of dried pupae, equivalent to the control of approximately 95,000 potential flies which are converted into fodder. However, the effect of attracting flies towards these media on fly populations elsewhere should be the object of further study. In Huancayo we plan to produce 3.6 t/a of dry fly flour and to commercialise it as a component in 25.5 t/a of concentrate, destroying 1,235 million potential flies per year.

Benefits of controlling flies

If poultry or other birds cannot be fed directly on the maggots or pupae, the manpower and other inputs required in production may outweigh the economic value of the fly flour. Even so, there are a number of other factors to be considered when controlling flies using the presented method:

• One single fly may carry up to 6,600,000 bacteria, 1,250,000 on average, and other micro-organisms (Hint and Metcalf, 1974). This makes flies ideal vectors for more than 20 human diseases like cholera, typhoid, dysentery, diarrhoea, poliomyelitis and several parasitic worms. Furthermore, they are intermediate hosts of worms harmful to animals (Graham-Smith, 1914). By massive control of flies, an important contribution to a healthy environment would be made, especially in countries with warm climates, preventing tropical diseases in humans and animals. That is why, in the context of public human and veterinary health, it is a very profitable method.
• Destroying the flies in their pupal stage of development is the most appropriate sanitary method, because at the pupal stage they are not infected with any diseases. They are virtually free of micro-organisms.
• The method described promotes creativity, is effective, simple, and does not involve the use of insecticides.
• Untreated manure is converted into compost.
• A word of warning: special care must be taken when placing the crates, that access by children is avoided due to the danger for hygiene.

Johannes Füssel and Ruben Paitan

Ruben Paitan, CEDEPAS, AP 430, Huancayo, Peru. Fax: +51-64-222 536
Johannes Füssel, APROCACAHO, Casilla 1235, San Pedro Sula, Honduras. Fax: +504-69-3829.