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DIY Fruit Fly Management

close up of a fruit fly

Small fruit flies are proving particularly annoying in Indiana, Kentucky, and Illinois this fall, even outdoors in some cases. A topsy-turvy year of weather with a mild winter, hot spring, summer drought, and wet fall may have proved a perfect storm. Melon crops are still in some fields and stands of corn left in fields due to drought loss or inability to harvest can provide ample outdoor sources. Whatever the reason, small fruit flies are quite the nuisance this year. However, their management is not chemical-based. It is best handled through sanitation, exclusion, and moisture control. Fruit fly management can prove quite frustrating as the source is not always immediately evident or simple to eliminate. Trapping alone simply removes the adult flies which are but a symptom of the real problem.

The following are a few simple methods for constructing some Do-It-Yourself fruit fly traps as well as recommendations to avoid and reduce fruit fly infestations.

  • Eliminate the source of fruit fly activity. Moist, fermenting organic matter is the preferred food source and breeding medium of small fruit flies. This may be fruit left out on a counter, dishes soaking in a sink overnight, a dirty garbage disposal or sink drain, an overwatered plant, compost bin, trash receptacle or compactor, standing water in a sump pit, leaking toilet seal, water accumulated in the refrigerator condensate pan. I observed fruit fly larvae in the bottom of a toothbrush holder where water from the bristles had accumulated in the bottom of the cup. It should be noted that removing the source will leave the adult flies to find another food source, like the garbage or your soda can. Multiple sources may also be involved. Fruit fly best management practices include leaving no dishes or drinks out overnight, sealing trash at night, and storing fruit inside the refrigerator.
  • Eliminate adult small fruit flies. Take a clean jar and place an attractant in it. This can be a few pieces of fermenting fruit, cider (or other) vinegar, grenadine, or beer. You may need to vary your attractants to find what works best for you. Stretch plastic wrap over the top and hold it in place with a rubber band or tape. Poke a tiny hole in the center of the plastic wrap large enough for one fly to enter (use a toothpick). Holes too large may allow the flies to escape. Dispose of your attractant outdoors at least weekly to avoid it becoming another breeding medium. Another method involves modifying a plastic bottle by cutting it in half, inverting the top into the bottom, and taping it in place. Unlike the picture, I recommend keeping the cap and poking a small hole in it. Place out multiple traps in areas of activity after you have located and eliminated the breeding site.