Fruit Flies are of the species Drosophila, typically pale yellow to reddish brown and black with red eyes. Many species have distinct black patterns on the wings. Most are small, about 2–4 millimetres long. Fruit flies can be a problem year round, but are especially common during late summer and fall because they are attracted to ripened or fermenting fruits and vegetables.
Tomatoes, melons, squash, grapes and other perishable items brought in from the garden are often the cause of an infestation developing indoors. Fruit flies are also attracted to rotting bananas, potatoes, onions and other unrefrigerated produce purchased at the grocery store. Fruit flies are primarily nuisance pests.
They are common in homes, restaurants, supermarkets and wherever else food is allowed to rot and ferment. Fruit flies lay their eggs near the surface of fermenting foods or other moist, organic materials. Upon emerging, the tiny larvae continue to feed near the surface of the fermenting mass. This surface feeding characteristic of the larvae is significant in that damaged or over ripened portions of fruits and vegetables can be cut away without having to discard the remainder for fear of retaining any developing larvae.
The reproductive potential of fruit flies is enormous. Given the opportunity, they will lay about 500 eggs. The entire lifecycle from egg to adult can be completed in about a week. Males are known to have the longest sperm cells of any organism on Earth. The cells are mostly tail and are about .25 millimetres long, although this is still about 100 times as long as a human sperm.
Fruit flies are especially attracted to ripened fruits and vegetables in the kitchen. But they also will breed in drains, garbage disposals, empty bottles and cans, trash containers, mops and cleaning rags. All that is needed for development is a moist film of fermenting material. Infestations can originate from over ripened fruits or vegetables that were previously infested and brought into the home. The adults can also fly in from outside through inadequately screened windows and doors.
The best way to avoid problems with fruit flies is to eliminate sources of attraction. Produce which has ripened should be eaten, discarded or refrigerated. Cracked or damaged portions of fruits and vegetables should be cut away and discarded in the event that eggs or larvae are present in the wounded area. A single rotting potato or onion forgotten at the back of a closet can breed thousands of fruit flies.
Once a structure is infested with fruit flies all potential breeding areas should be located and eliminated. Unless the breeding sites are removed or cleaned, the problem will continue no matter how often insecticides are applied to control the adults. Finding the sources of attraction and breeding can be very challenging and often will require much thought and persistence. Potential breeding sites which are inaccessible such as garbage disposals and drains can be inspected by taping a clear plastic food storage bag over the opening overnight. If flies are breeding in these areas, the adults will emerge and be caught in the bag.
One way to get rid of fruit flies is to construct a bowl trap by placing a piece of old skinless fruit and some wine or some balsamic vinegar in a bowl. Cover the bowl tightly with plastic wrap and a rubber band, and poke many small holes in the plastic with a fork. The fruit flies go in and can’t get out, but if the holes are too big they will be able to escape. Release the flies outdoors and dispose of the bait.
Another approach is to construct a trap by placing a paper funnel rolled from a sheet of notebook paper into a jar which is then baited with a few ounces of cider vinegar. Place the jar traps wherever fruit flies are seen. This simple but effective trap will soon catch any remaining adult flies which can then be killed or released outdoors.