While fruit flies have the potential to be a year-round problem, they cause the biggest misery from mid-summer into fall, when fermenting vegetables and fruit are most abundant.
Fruit flies are in the family Drosophila sp. The flies are very tiny, about an ⅛ inch long. Some call them vinegar flies, pomace flies or kitchen gnats. If you can get close and personal with them, you may notice the red eyes or the black and tan body.
These flies are common anywhere there is ripening or fermenting fruit. You may even see a couple at the grocery store hovering above ripened bananas. Right now they are common in my own kitchen, where a couple of tomatoes were left on the counter past their prime.
Fruit flies are attracted to fermenting vegetables and fruit — organic matter — because this is where the flies lay their eggs. The eggs are laid on or near the surface of the rotting parts of fruits and vegetables, and if you think the flies are small, the eggs are only 0.5 mm long.
At optimum conditions, it doesn’t take long for the eggs to hatch, about 24 hours. The larva immediately start eating at or near surface of the rotting areas of the fruit. Because of this, it is acceptable to cut off overripe portions of fruits and vegetables and consume the rest. The larvae begin to pupate near the food source. The adult flies that we see swarming around our garbage cans and food sources emerge. The whole life cycle is completed in a week. A female fly can lay up to 500 eggs in her life. Now you see why the population seems to explode in the kitchen.
Once the life cycle of the fruit fly starts indoors, it can escalate quickly. They are usually brought in from overripe fruit in the garden. Fruit flies can also come in when windows are open and through cracks in windows and doors.
The best thing to do is avoid the situation by quickly disposing of over-ripened fruits and vegetables. A compost pile is one of the best ways to dispose of the vegetables. Also, store fruits and vegetables properly — preventative measures go a long way.
Once a fruit fly problem is established, several methods must be used to reclaim your kitchen:
• Any and all breeding grounds should be eliminated. This means clearing the counter and pantry of all ripening vegetables that could be breeding stations for the fly.
• Take trash cans out and wash them. Any scrap left in the garbage can or stuck to the sides is a potential breeding site.
• Kitchen drains, especially disposals, should be cleaned. Using a brush to remove food residues on the drain sides as well as using boiling water down the drain can help eliminate sites.
• Even mops could serve as breeding sites if debris from the kitchen floor is on the mop.
• Pyrethrum-based insecticides labeled for indoor use can be used to control adults, but remember the many eggs that are yet to hatch.
• A simple trap can be used in the kitchen and other rooms in the house where fruit flies have become a problem. (Fruit flies originating in the kitchen may find solace in the bathroom where they are attracted to the moisture.)
To make a trap, you will need a jar, a piece of paper and some cider vinegar (I know others who have used slices of banana, as well as wine). Roll the sheet of paper into a funnel. Pour a couple of inches of the vinegar into the jar. Insert the funnel into the jar.
The adult flies are attracted to the vinegar. They fly into the jar through the funnel, and are unable to fly out. I would put one wherever fruit flies are seen in the house. You will see the population diminish quickly.
Now I’m off to reclaim my kitchen!
Danielle Carroll is an extension agent for the Alabama Cooperative Extension System.