How to Get Rid of Fruit Flies Organically

Every autumn, when fruit flies are drawn to my kitchen by the aromas of apples and pears, I think of still life painters like American artist Levi Wells Prentice, whose favourite subjects were slightly over-the-hill apples. How did painters keep fruit flies from swarming their set-ups? Were the flies repelled by the smell of oil paints?

At my house, fruit flies are a constant nuisance in fall when I’m harvesting and processing apples and pears. They are welcome outdoors in the compost, but my tolerance for fruit flies in the kitchen is extremely low.

What Are Fruit Flies?

Recent research indicates that fruit flies (Drosophila melanogaster) started hanging out with humans more than 10,000 years ago in Africa, where they developed a liking for plumlike marula fruit. Since the early 1900s, fruit flies have been used as animal subjects in the study of genetics and neuroscience because they reproduce rapidly and are easy to keep. The largest fruit flies are only 1/8 inch (3–4 mm) long, and they are distinguished by their big red eyes, which you can see with a hand-held 10x magnifying glass.

Fruit flies do not bite or sting, but they are wild about mating and reproducing. One female can lay up to 100 eggs, and the time from egg to maturity can be as short as 10 days. This is how an apple core forgotten in a wastebasket gives rise to a colony of fruit flies. A countertop compost pail filled with pear parings is fruit fly heaven.

Preventive Controls for Fruit Flies

Sound fruits are of no interest to fruit flies, because the young feed on compounds produced by rotting fruit. When allowing apples or pears to finish ripening indoors, check the fruits daily for signs of trouble. The presence of fruit flies will lead you to advanced rot spots or other serious problems, which often start near the bottoms of apples or pears.

It’s also important to empty and clean your countertop compost container often, because fruit fly eggs can persist in the slick organic material left stuck to the sides. Dump your compost in the evening when possible so there is no decomposing fruit present first thing in the morning, when fruit flies are most active.

Should you notice fruit flies in your kitchen sink, try this advice from Laurie Stevison, assistant professor of biological sciences at Auburn University. Pour hot water down your drain, then cover the drain and fill the sink with water. Leave the water in the sink overnight to kill the flies by depriving them of oxygen.

Simple Fruit Fly Traps

Fruit fly traps are easy to make because fruit flies are easily attracted by compounds given off by fermenting fruit, including acetic acid in vinegar. Several studies have shown that apple cider vinegar is a more potent attractant compared to wine, beer, or fermenting sugar water. The lure in commercial fruit fly traps is basically vinegar.

Fruit fly traps require the addition of liquid soap which causes the trapped flies to drown. Without two drops of soap swished in, fruit flies will come back to life after lengthy swims in vinegar.

Any small container with a narrow neck makes a good fruit fly trap, including bottles, jars, or small vases. Small canning jars make great fruit fly traps, and this is a wonderful re-use for canning jar lids. Use a hammer and nail to make five small holes in a lid through which the fruit flies can enter. Place a finger’s depth of cider vinegar and two drops of dish soap in the jar, screw on the lid and you’re good to go.

Controlling Fruit Flies in Compost

Outdoors, fruit flies are beneficial insects that aid in the decomposition of fruits. Fruit flies are generally welcome in open compost piles, but they can become so numerous in enclosed composters during fruit season that you’re reluctant to open the lid. Adding fresh grass clippings can help bring populations down quickly. Also temporarily divert excess fruit waste to holes or trenches dug in the garden. In addition to helping to control fruit flies in compost, burying fruit waste makes your compost less attractive to curious wild animals.

Photo at top of page by AfroBrazilian.