Fruit Flies

Fruit fly trap in covered box

In late summer, when so many people are bringing harvested fruits and vegetables in from the garden, or home from the farmer's market, is the time when we are most likely to find tiny gnat-like insects flying around in our kitchens.  These tiny insects are fruit flies.  They are brought into our homes as unwanted guests on the fresh produce, or are drawn to the smell of the produce, and squeeze in through even very small cracks around windows or doors.


There are many different species of fruit flies, and they are found all around the globe. Some species prefer specific foods, but in general they feed on any decaying matter, especially fruits and vegetables. They are very small insects, and tiny scraps of food are enough to support them.  Wet mops and kitchen sponges will have small particles of decaying matter on which they can feed. Even the scum inside the kitchen drain or garbage disposal is enough.

Fruit flies lay eggs in whatever food they're eating.  Eggs usually hatch in less than a day, possibly in just a few hours.  The larval stage usually lasts about 4 days, then there is the pupal stage before emerging as adult flies. The entire process from egg to adult generally takes 14-30 days, but can be completed in as little as 8 days.

Because fruit flies are drawn to decaying matter, such as in garbage cans, they can carry disease-causing bacteria onto food.

If any produce has damaged or exposed areas, that will draw fruit flies to feed and lay their eggs.  Because the larvae stay near the surface of the food, a person can cut off that damaged area of the fruit or vegetable and eat the remainder without fear of retaining any larvae.  Eating the larvae can cause intestinal discomfort and diarrhea.

To control fruit flies, the most important thing is to deprive them of a breeding place.  When possible, store fruits and vegetables in the refrigerator rather than out in the open.  Any that aren't refrigerated need to be carefully checked to remove any that are decaying. Keep kitchen surfaces well wiped. Scrub out garbage cans, dumpsters and recycling bins, and make sure they have tight-fitting lids. Replace your kitchen sponge and mop refill periodically.

Cleaning kitchen drains is important in controlling fruit fly infestations.  Pour boiling hot water down the drain weekly or whenever they begin to slow to help loosen accumulated deposits.  Don't depend on bleach for this, as it will help disinfect, but doesn't remove the scum fruit flies feed on.

After removing any potential food sources and breeding places, you can also use traps to catch adult flies.  There are commercially-available insect traps made especially for fruit flies.  You can also use sticky fly paper.  But there are simple traps that can be made with common household items at no cost.

My favorite fruit fly trap is to put apple cider vinegar in a shallow cup, and add a few drops of dishwashing soap.  The soap is essential, as it breaks the surface tension of the vinegar, so that flies drawn to the vinegar will drown in it.  I keep this little cup in a small stone box with a perforated lid.  That way I don't have to look at it, but the flies can get in.

Some people use a sheet of paper rolled to form a funnel down into a glass or jar, with apple cider vinegar as bait in the glass.  The flies follow the smell of the vinegar to get in, but few find a way out. You can also use an old plastic funnel set on a glass or jar.

Or cover a baited jar with a plastic baggy, rubber-banded to hold it in place, and then poke a small hole in the middle.  A toothpick makes the right size hole.  Others use an old salsa jar, with a few holes poked in the lid.  The most effective baits for such traps is apple cider vinegar, or wine. 

Leave your trap for a few days, then check it.  You should see dead fruit flies in the vinegar.  Empty your trap as needed, and refill with fresh vinegar and dishwashing soap.

Fruit flies can invade your home at any time of year, but as fall is coming, be especially alert and ready to keep a small problem from becoming a major nuisance.