vinegar fly on berries
Close-up view of a vinegar fly (Photo credit: John Obermeyer)

Is it that time of year already? Summer is gone and fall is here. Temperatures are cooling, leaves are beginning to turn color, vegetables from the garden and fruits from the orchard are ready for harvest, and fruit flies are flying throughout the kitchen. These are all signs that autumn is upon us. Wow! Where did the time go?

An old adage goes something like "time flies like the wind." How true it is. However, a similar and equally true saying - no doubt coined by the kitchen staff - goes something like "fruit flies like bananas." 

Time flies like the wind, but fruit flies like bananas! Both statements are true and both warrant deep reflection. But what is their relationship? 

Gardeners are now finally and proudly bringing their bounties of fruits and vegetables into the home for eating or processing, but in so doing, they often also accidentally introduce eggs or larvae from a nuisance pest called a fruit fly, or more properly, a vinegar fly. In their adult stage - when they really become noticeable - they appear as tiny brown- or black-colored flies, about 1/8 inch in length, that usually have red eyes, if you look really closely. And, while you are looking closely - and I mean really closely - look for black striping on a yellow abdomen. That will confirm them for sure. 

Most people don't really take the time to observe vinegar flies all that closely, because they are busy shooing them away from their food. So, just spotting tiny flies around ripening fruits or vegetables in the fall is enough to give a pretty accurate diagnosis. 

The biggest complaint from most people is that these flies are a nuisance pest. They fly around just about anywhere fresh food is stored, washed or prepared. They land on nearly everything, and fly about our heads and faces. They are just really … well … pesty. 

Vinegar or fruit flies can be pests year-round, but are especially meddlesome during the late summer or fall because that is when fruits and vegetables, including tomatoes, melons, squash, grapes, apples, peaches, or just about any other perishable items, are brought in from the garden. They usually begin out of doors where they lay tiny eggs in the cracks or folds in the produce. Eggs hatch into tiny white larvae that invade the flesh of the fruit or vegetable. When infested produce is brought into the home, the maggots complete their development and emerge as adult flies, ready to reinfest any overripe fruits or vegetables stored on the countertops. 

They may also be brought home via ripened bananas or other produce from the grocery store, and once in the home, they are experts at finding foods to eat, such as rotting potatoes, onions that have been forgotten in the back of the pantry, or even small amounts of fermenting juices that may have been spilled behind sinks or counters. In fact, they can breed in empty bottles and cans in the recycling bin, or even dirty mops and cleaning rags. All that is needed for development is a moist film of fermenting material. Clogged drains or garbage disposals, or dirty trashcans are equally adequate for the flies, and this is where the even bigger problem lies. Vinegar flies have the potential to spread nasty bacteria and other disease-producing organisms from garbage to the foods we are eating. 

Regardless of where they originate, once inside a home, their reproductive potential is enormous. Given the opportunity, a female, assuming she has already been out on a date with a male fruit fly, can lay about 500 fertile eggs. That is a huge number of eggs for a tiny fly. Now - and here is the really mind-blowing fact - an entire vinegar fly life cycle (from egg to adult) can be completed in as little time as one week. 

Pull out your calculators for a moment. This means that one particular pregnant fruit fly can lay eggs on October 1, and if all 500 eggs could hatch and develop through their customary larval and pupal stages, they would become 500 flies by October 7. Each of these could easily find a mate and, assuming that half are females, could produce 125,000, if all conditions were just right, by October 14. Anybody working or eating in the kitchen will notice a problem by this time and will have taken action. 

But just for the sake of this story, let's say that these 125,000 all remained undetected, healthy and had plenty of breeding sites to feed and lay eggs. If so, there could be 62.5 million by October 21 and more than 15.5 billion by Halloween. Even your typical, unobservant, couch potato type husband should have noticed a problem by that point. 

But fly populations don't get that big, that quickly, in most cases. Not all eggs hatch, nor do all larvae survive to reproduce. In most cases, someone will have nagged the husband enough that the garbage will have been taken out, and the available breeding and feeding resources will have been removed well before then. 

This is actually the best way to avoid problems with vinegar flies: not with aerosol pesticide sprays, but rather by eliminating the availability of food and breeding sites. Produce that has ripened should be eaten, discarded, refrigerated or processed. Leaving it sitting out on the countertop for an extended length of time is asking for trouble. Accumulating trash, especially trash with organic material in it, is risky. Even small spills, dirty trash containers, or cans or bottles that have not been rinsed out, can be enough to produce large numbers of flies. 

Once a home is infested with fruit flies, all potential breeding areas must be located, cleaned or eliminated. Unless these breeding sites are removed, the problem will continue, no matter how often insecticide sprays are applied to control the adult flies. This can be very challenging, and will require persistence on the part of the homeowner. 

After all breeding sites have been eliminated, homeowners may want a solution for the pesky swarm of flies that continues to hover in the kitchen, wondering where their food source has gone. A couple of options in addition to the aerosol pesticides, may help. 

A vacuum cleaner can suck them up quite readily. Even a DustBuster in the hands of a determined homeowner is bad news for vinegar flies. This sometimes becomes an obsession, and even though a bit time-consuming, feelings of great triumph are often reported by humans searching for, carefully stalking and, at the last second, sucking up the odd, unsuspecting fly. 

Once all other sources of food are removed, homemade vinegar fly traps, consisting of a few ounces of apple cider vinegar and 1/2 teaspoon of dish soap in an open dish or bowl can be effective when placed near where the swarms persist. The flies are attracted to the smell of the vinegar (why they are often called vinegar flies - duh), and will attempt to land in the bowl, but because of the soap, the surface tension of the vinegar is reduced and the unsuspecting flies drown in the very irresistible, intoxicating liquor that they crave. (Not a bad way for a vinegar fly to go - if you really think about it.) 

Next to actually hunting the flies with the vacuum cleaner, this method is very popular and reportedly brings great satisfaction for the homeowner. In fact, some are known to check the trap last thing at night before going to bed, and actually wake up early in the morning just to count the number of flies removed during the nighttime. Cheers and fist pumps follow, usually in direct proportion to the number of flies caught times the amount of annoyance that the flies have caused. 

So, the take-home message is simple. Always remember that ripe fruits and vegetables, plus even a short period of time, equals fruit flies. It is basic entomological mathematics. 

Or, if it is easier, just remember the old adage "time flies like the wind and fruit flies like bananas."