ENTFACT-621: Fruit Flies | Download PDF | En Español
by Michael F. Potter, Extension EntomologistUniversity of Kentucky College of Agriculture
Fruit Fly
If you have been seeing small flies or gnats in your kitchen, they're probably fruit flies. Fruit flies can be a problem year round, but are especially common during late summer/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. This fact sheet will explain how infestations originate and how they can be prevented in your home or place of business.
Biology and Behavior
Fruit flies are common in homes, restaurants, supermarkets and wherever else food is allowed to rot and ferment. Adults are about 1/8 inch long and usually have red eyes. The front portion of the body is tan and the rear portion is black. 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.
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.
Fruit flies are primarily nuisance pests. However, they also have the potential to contaminate food with bacteria and other disease-producing organisms.
Prevention
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, or fruit juice spillage under a refrigerator can breed thousands of fruit flies. So can a recycling bin stored in the basement which is never emptied or cleaned.
People who can their own fruits and vegetables, or make wine, cider or beer should ensure that the containers are well sealed; otherwise, fruit flies will lay their eggs under the lid and the tiny larvae will enter the container upon hatching. Windows and doors should be equipped with tight-fitting (16 mesh) screens to help prevent adult fruit flies from entering from outdoors.
Eradication
Once a structure is infested with fruit flies, all potential breeding areas must 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 source(s) of attraction and breeding can be very challenging and often will require much thought and persistence. Potential breeding sites which are inaccessible (e.g., 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.
After the source of attraction and breeding is eliminated, a pyrethrum-based, aerosol insecticide may be used to kill any remaining adult flies in the area.
Fruit Fly Trap
A better approach, however, 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 trap(s) 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.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
Images: University of Kentucky Entomology
Overview
Are there extra guests in your kitchen that you didn’t invite? Are they buzzing around your fresh fruit and vegetables, or even your trash can? Maybe you left out some empty beer bottles and they’re flying around those, too? If you answered yes to any of these questions, you may have a fruit fly infestation in your home.
Here are seven things you can do to help get rid of these pests.
The first thing you need do is figure out where the flies are coming from. If they’re hanging out around any open food items, throw the food out and scrub the area clean. You can use any type of cleaner to disinfect the area. In some cases, removing their “home” can be enough to drive the fruit flies away.
After you’ve found the source of the problem, check out the drain in your kitchen sink. If it’s clogged or in need of a good cleaning, now’s the time to take care of it. Fruit flies like to live and breed in warm, damp spaces.
Don’t forget to check your trash cans for any signs of fruit fly activity. Fruit flies have been known to lay their eggs in trash cans, worsening the infestation.
If they’re swarming around your trash can or if you’d like to prevent such a situation, take out the trash and wipe down the can using a heavy duty cleaner such as bleach. Make sure the cans are completely dry before using them again.
If you still spot fruit flies hanging around, you can set a trap using things that you may already have in your kitchen. This includes any rotten or open food that attracts fruit flies. Follow these steps:
- Instead of tossing out the rotten or open food, put the food in a disposable container.
- Cover the container with plastic wrap.
- Poke a few holes in the wrap, place it where fruit flies congregate, and wait.
The flies should swarm to the inside of the trap. You can then dispose of them how you see fit. Repeat this process until all of the fruit flies are gone.
Have leftover red wine that you don’t plan on finishing? Use it to create a swimming pool trap for the fruit flies. Here’s how:
- Pour some red wine and dish detergent into a disposable container and stir.
- Cover the container with plastic wrap.
- Poke small holes in the plastic wrap. Make sure the holes are big enough for the fruit flies to get in.
The wine should attract the fruit flies, and the combination of wine and dish detergent will make it difficult for trapped flies to fly and will drown them. You can repeat this process until you no longer see any more fruit flies.
You can also try to attract fruit flies by making a vinegar trap. Here’s how:
- Fill a disposable container up with water.
- Add a few tablespoons of vinegar and sugar to the water and stir.
- Add a few drop of dish soap to the solution and stir.
After mixing your solution, place the container wherever the fruit flies congregate. They should be attracted to this solution and will drown once they touch the water. Continue this method until you no longer see any fruit flies.
If homemade traps aren’t working for you, visit your local hardware store and purchase a sticky fly trap. These traps work on common flies and fruit flies.
Place the trap in the problem area and dispose of it once the sticky area is full. You can replace the trap as necessary.
Hiring an exterminator should be your last resort. Although this is usually effective, it can be costly. You or your pets may also experience adverse reactions to the chemicals used to get rid of the fruit flies.
If the fruit flies return after your house has been treated, the company may treat your home again for a free or reduced rate.
Learn more: Fruit and vegetable safety »
If left untreated, a fruit fly infestation can pose potential health risks. Fruit flies are known to fly around and pick up bacteria that they then deposit onto fresh foods.
They’re particularly drawn to manure and other feces that can contain bacteria such as E. coli. They then carry the bacteria with them.
Additionally, after mating, female fruit flies inject batches of eggs into fresh fruit. This contaminates the fruit.
To prevent future infestation, be sure keep food storage areas clean and dry. Don’t leave out fresh food once it’s been opened or after you’ve taken a bite out of it. Be sure to take out your garbage regularly and clean up any spills inside or on your trash bins.
Once you have a fruit fly infestation, it can take anywhere from a few days to a few weeks to get rid of the nuisance. By taking proactive steps in cleaning and trash disposal, you can save yourself the time and hassle.
Keep reading: The 9 dirtiest spots in your home »