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Tiny, Red-Eyed Flies Flitting Around Your Fruit?

The Fruit Fly

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Tiny, Red-Eyed Flies Flitting Around Your Fruit?
Joseph Berger, Bugwood.org

The fruit fly (often called a gnat) is one of the most common, and one of the smallest flies found in the home. It is often unknowingly brought into the home on fresh fruits and vegetables.

If you can get close enough, you can easily identify this tiny fly by its proportionately large red eyes. In addition, it:

  • is about 1/10 to 1/5 inch in length.

  • has a yellowish-brown to brown body.

  • has black rings across its abdomen.

(Of course, at 1/10 inch long, a magnifying glass or microscope will be needed to see these minute characteristics.)

Fruit Fly Facts

  • Though commonly called a fruit fly, its technical name is vinegar or pomace fly, or even more scientifically Drosophila fly (multiple species).

  • As you would expect by its common name, the fruit fly feeds on overripe fruits, rotting vegetables, fermenting liquids such as soft drinks and alcohols, and other fermenting foods in garbage and drains. Because they are attracted to the yeast in the foods, they may also be hovering around or landing on breads and other baked goods.

  • However, its technical name is just as appropriate, as the fly is also highly attracted to vinegars and pomace – the pulpy residue left from the crushing of fruits.

  • Because of the abundance of harvested fruits in late summer and fall, fruit fly populations generally peak at that time as well.

Fruit Fly Damage

Though primarily a nuisance pest in homes, the fly can damage harvested fruits and carry sour rot organisms to damage vineyards.

This fly can be of particular concern in the harvesting of strawberries to be picked for freezing. Because the fruit is left in the field to ripen, it becomes attractive to the fruit fly while still on the plant, thus making the fruit particularly susceptible to fruit fly damage.

With the amounts of fresh produce brought into restaurants and the potential for build-up beneath soda fountains and beer taps, these facilities are also highly susceptible to fruit fly infestations. The key to prevention and control is the same as in the home: sanitation and removal or potential feeding sites.

Fruit Fly Control

As with most flying insects, control of this fly is best achieved by identifying then removing the source of its feeding and breeding:

  • Discard or refrigerate ripening fruits.
  • Clean any spilled juices, sodas, or other liquids.
  • Wash out beverage containers before recycling.
  • Clean garbage and trash containers and areas.

A household, pyrethrin aerosol can kill the adult flies, but it will not affect the larvae. Thus repeated application would be necessary until all feeding/breeding sites and matured adults are eliminated. When using any pesticide, always read and follow all label directions.

Once all feeding/breeding sites are cleaned or eliminated, it can also be effective to simply wait them out, particularly in outdoor areas, because as suddenly as a population appeared, it can disappear when the weather turns cold.

Commercial Control

Commercial control has been achieved through pesticide application, fumigation, and, on a trial basis of tropical fruit shipped from Hawaii to the mainland, irradiation.

In addition, research funded by the National Science Foundation has shown that control can be achieved by attuning oneself to the insect's natural biorhythm. According to the research: "The researchers tested the flies' sensitivity to various pesticides at different times of the day and found that the levels needed to kill the flies varied with the time of exposure. This sensitivity was reflected in gene activity associated with the circadian clock. For example, a group of genes appears to peak in late afternoon, causing the flies to have the most resistance to chemical exposure at this time."

The results of the study, led by Jadwiga Giebultowicz of Oregon State University, suggest that pesticide use should be associated with time of day to achieve the best results and use the least chemical.

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