FLY and OTHER PEST CONTROL
One of the most important problems in composting is controlling flies. Garbage, animal manure, tomato and several other food-processing wastes, are excellent media for breeding and development of large fly populations. If adequate control measures are not practiced, particularly when composting manure, the compost systems will be infested with extremely large numbers of flies, and create a health hazard.
Fly-breeding can be satisfactorily controlled in composting operations during the fly season, with little more effort than is normally necessary for good sanitary composting. Added manure and fresh food scraps in the composting systems should be kept covered.
Fly larvae in composting material may originate from eggs laid in the material at the place of collection or from eggs laid during the handling of the material at the compost site. If the latter were the main source, fly control would be no problem. However, much of the material is infested with eggs and larvae in various stages of development, sometimes even at the pupal stage, before arriving at the compost site. Therefore, material must be prepared immediately for composting and placed in compost systems where high temperatures and environmental conditions are unsatisfactory for continued emergence of flies.
The predominant species of flies encountered in composting will vary with the area and with the type of material. The variety of materials available for composting offers satisfactory breeding conditions for many different species, but generally speaking, the compost operator does not have to interest himself/herself in the particular species, since the most satisfactory control measures in composting apply equally well to different species.
The life cycle of the ordinary housefly, " musca domestica," is usually from about 7 to 14 days when conditions are favorable. The time of the different stages varies with temperature and other conditions, but on average it may be considered as follows: egg, 1 to 2 days; larva 3 to 5 days; pupa, 3 to 5 days; emergence of young fly, 7 to 10 days; and egg laying by new fly, 10 to 14 days. Fly control measures must interrupt this cycle and prevent the adult flies from emerging.
Some procedures, particularly grinding, turning, and systematic cleanliness, which are useful in providing compost of good quality and in destroying parasites and pathogens, are also effective for controlling flies. Initial shredding or grinding to produce material more readily attacked by bacteria also destroys a large number of the larvae and pupae in the raw material. Also, the texture of material shredded to a maximum size of 2 inches is not as suitable for fly breeding.
Studies at the University of California on mixed garbage and refuse demonstrated that after raw material containing considerable numbers of eggs and larvae had been ground and placed on the pile, no fly breeding took place using normal composting procedures of turning every 2 to 3 days. Apparently, the destruction of the larvae by grinding, mixing, and the structural changes caused by grinding, results in garbage that is no longer attractive to flies. Heat quickly generated in compost piles effectively stops flies breeding in refuse containing a considerable proportion of garbage. However, this is not the case, for compost materials containing large amounts of animal manure, food scraps and other fresh and decaying fruits.
When materials attractive to flies and containing large numbers of larvae and pupae are composted, some of the larvae will move to other cooler layers and continue their life cycle. The most effective method of destroying these larvae is frequent turning. Turning compost stacks at daily interval, when the raw material contains many larvae and pupae and when fly breeding conditions are favorable, and at a maximum interval of 3 or 4 days when fly breeding conditions are not especially favorable, provides good fly control.