UF/IFAS Okeechobee Extension Service Vinegar Fly

Add another annoyance to the list of hurricane-related problems faced by our area. A visit to the local produce section of your favorite supermarket may introduce you to another unwanted friend, courtesy of Frances and Jeanne. With an abundance of moisture and decaying vegetation, area homeowners are now having to deal with pesky "fruit flies".

These insects are not the ones that our grove owners are protecting their citrus crops against, rather, they are more properly called vinegar flies. Rotting fruit produces yeast, which is the favored foodstuff of this household pest. Contained in your shopping bags of fruits or vegetables may be several of these hitchhikers who then gain entrance to your kitchen or pantry. They may also gain a foothold from your garden due the absence of window screens which were damaged or blown away.

It’s not much of a consolation, but other areas of the country are also facing outbreaks of these pesky insects - I found an article published at the end of September in Olympia Washington; they too were bothered by swarms of vinegar flies this summer. The speculation is that warmer than normal temperatures increased their "fruit" fly population by 70%.

Electron Micrograph of Vinegar Fly's face

Adult Vinegar Fly - note eyes, antennae, and wings Photo (above and right) by Jack Kelly Clark, University of California

Vinegar Fly maggot (larva)

Let’s be sure we are talking about the same thing. Vinegar flies are about 1/8" in length, brownish-black to brownish-yellow in color and have a feathery bristle on the antennae. They typically have red colored eyes and two very small wings that allow them to quickly hover in on both fresh fruit and decaying vegetable matter. These insects are called by their scientific name, Drosophila melanogaster, and are favorites with researchers studying genetics because of many variations in body structures.

There are several other small flies that may be confused with vinegar flies. Eye gnats, hump backed flies and moth flies are generally darker in color and are more fond of decaying waste materials. The vinegar fly is also smaller than any of the real fruit flies, such as the dreaded Medfly or Caribfly. If you are unsure what is winging in your wine or festering in your fruit, capture a couple and bring them in a closed container to our office for positive ID.

Drosophila typically have a short life cycle. Each female lays about 500 eggs which hatch into maggots (larvae) that mature to adults in 9-12 days. Keeping fly free for 2 weeks will break the infestation in local areas.

According to UF Entomologist Phil Koehler, sanitation is the best way of controlling vinegar flies. Flies will seek breeding places where garbage, manure, or vegetation residues accumulate. Dropped fruit, dirty garbage containers, or slime in drains provide organic materials that support the yeasts that grow on organic matter.

Locate and thoroughly clean such places. Do not let garbage accumulate in the open. Make sure garbage cans have sound bottoms and tight fitting lids. Good fitting screens on windows and doors are essential in preventing flies from entering homes and kitchens. In areas with high humidity screens last longer when made of aluminum, plastic, or fiberglass. Choose a mesh of 16 or more to be sure that the screen holes are smaller than the flies.

Where flies are present, traps can be purchased or constructed to trap vinegar flies. UF Entomologist Dr. Roxanne Rutledge-Connelly says they can be built by nesting a small bowl of fly bait - wine or balsamic vinegar - in a larger bowl of sudsy water. Some of the flies attracted to the bait will land in the water and get trapped in the bubbles. Check our website for a couple of other ideas for home made vinegar fly traps.

Courtesy: University of Kentucky

Courtesy: THE Ohio State University

While I’m not sure of how effective they will be, the folks out in Washington state were flocking to their specialty plant shops to purchase carnivorous plants - sundews and pitcher plants that capture and consume insects were very popular out there with fly infested homeowners. (Venus Fly traps were not mentioned as useful for vinegar flies - see photo!)

In the yard, be sure to keep compost piles covered with leaves and soil until the clouds of vinegar flies abate. Cleanup any remaining fruit that the hurricanes have knocked to the ground and keep up with other fruit which drop.

Chemical insecticides are not a good idea to deal with vinegar flies in the kitchen - the potential for contaminating food or kitchen utensils and preparation surfaces is great. In the Florida Yard, the use of approved insecticides may be a way to complement cleanup efforts that will break the reproductive cycle of these flies. Contact our office if you would like recommendations of specific products that are labeled for vinegar fly control.

Master Gardeners can answer your questions about your Florida Yard - call or visit them on Tuesday afternoons here at our office. If you need additional information on vinegar flies, visit out webpage at http://okeechobee.ifas.ufl.edu , or stop by our office at 458 Hwy 98 North. Our phone number is (863) 763-6469, and you can email us at okeechobee@ifas.ufl.edu .

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