Biological pest control includes ecological measures and some quite high tech interventions. The principles behind it are encouraging predation of the pests by other animals, distracting or luring the pests away from your crops and decreasing the fertility of the pest, in this case fruit fly.Increasing the biodiversity of the garden is the first step to natural pest control, by encouraging the natural enemies of the pests to multiply. The way we can influence this as gardeners is with plant diversity, and increasing the habitats suited to insects, spiders and birds. For example, as opposed to naked earth, groundcover in orchards gives shelter to beetles, and ground and rove beetles feed on the
pupae of fruit flies, as do scratching insect eating birds. Birds and a diversity of insects and spiders like undisturbed areas of vegetation, hedges, creepers, groundcover and trees. Bird trays increase the garden’s birdlife. I put out birdseed, or hamster seed, scraps from the table like pumpkins skins and old fruit, and a little fat from boiling the dog’s bones. This and plenty of water, lead to us having masked weavers, two kinds of doves, two kinds of sparrows, wagtails, white eyes, ibis, Cape robins, and starlings constantly and a small changing population like sunbirds, when the aloes are flowering, sugarbirds and crows.
Flycatchers, Wagtails, swallows, spiders, robber flies and dragon flies catch the adult fruit flies, braconid wasps parasitize the eggs and ants and ground beetles eat the maggots.
You can introduce chickens which will also feast on the maggots in fallen fruit, and scratch up the ground to find pupae, and recently emerged adult flies. You can use mobile fencing if you need to confine the chickens.
You can liberate parasites of the fruit fly in the orchard, such as wasps which lay eggs in the larvae. In Hawaii the braconid Fopius arisanus and Pysttalia fletcheri were successful in halving the fruit fly population in a fruit fly suppression campaign that included biological pest control. Nematodes parasitic on the pupae can be released around fruiting plants on the ground. You will have to google to find
local suppliers of specific organisms that control fruit flies. In California it is the Environmental Protection Agency of Pesticide regulation Environmental Monitoring and Pest Management which can apparently supply you. Furthermore, irradiated and thus infertile male flies can be released. They will compete with other males to mate with the females and reduce the numbers of fruit flies. This has worked with a number of other insect pests, right up to tsetse flies and disease bearing mosquitos.
The way you plant will also influence the fruit fly
population levels. Plant your crop plants in mixed rather than extensive
plantings, and according to permacultural pest management, the insect pests do
not find your crops as easily, as they are interspersed with other plants and
distracting strong smelling plants which may mask
the odours of crops they feed on. Also surround your fruit and vegetables with plants
known to lure fruit flies away from your crops, such as lush shady bushes in a