Ask George: What can restaurants and bars do about the presence of fruit flies in their establishments?

What can restaurants and bars do about the presence of fruit flies in their establishments? —Teo V., St. Louis

Recently, in a local restaurant, the questioner noticed two fruit flies hovering above a salad that was just served. She lost her appetite, “assumed the kitchen was dirty,” and wanted to know what options she and her guests had in such a situation.

Let’s address the last concern first. Anytime a customer has an issue in a restaurant (with the food, beverages, environment), they should bring it to the attention of a manager, who should attempt to right the wrong, perceived or otherwise. Apologies are typically offered, items get comped, gift cards get issued—whatever it takes to keep the customer happy. In this case, since fruit flies can spread E. Coli and other unwanted bacteria and pathogens onto food, the questioner’s concern is legitimate.

The presence of fruit flies does not necessarily indicate a dirty kitchen, however, since fruit flies are airborne and can enter an otherwise clean establishment on a fruit, produce, or even a liquor delivery, and they can breed on any sweet, ripe, rotting, or fermenting products that are present. (Other unwanted critters can arrive by the same means, as was discussed in this column.)

Regarding the prevention and control of fruit flies, we spoke with Frank Meek, a board-certified entomologist with the entomology department at Rollins Pest Control, the parent company of Orkin and other pest control companies in the United States and worldwide. (Rollins has two local offices in metro St. Louis, one of which deals only with commercial accounts.)

Meek first points out that “fruit flies are not gnats. There’s no such thing as a gnat.” What people are seeing are three types of small flies—two fruit fly species and phorid flies—that all look similar and behave largely the same except for what they feed upon. “They all prefer different foods,” he says, “which means they don’t compete and can all thrive simultaneously,” so they can all exist in the same space. He adds that such flies can be present year-round, but the warmer the environment (such as the interior of a restaurant, bar, and kitchen), the more prolific they’ll be.

Meek says there’s no prophylactic or permanent chemical control for fly management. “You can’t stop them from coming in because they do fly, they travel well, and hitchhike well,” he says, before making his biggest point: that the best preventative is an ongoing sanitation program. Establishments should keep fruits and vegetables under refrigeration (as opposed to storing them in open air) and dispose of overripe product, as well as keep sinks, drains, and wastewater traps free of debris. Once flies enter an establishment, Meek says, the flies will die within the adult’s 10-day life cycle if there are no breeding grounds (i.e., decaying organics). 

Once consulted, the pest control professionals determine the location of the sanitation breakdown and treat the area with one or several products. Meeks says the best option is a biological product containing enzymes, bacteria, and surfactants, all of which are necessary to maintain the environment and eliminate breeding sources. (He cautions that some products on the market are bacterial-only, or enzymatic-only, which may not effectively control the problem.) The triple-action product can be used in conjunction with an insect growth regulator, which helps to break the life cycle and establish quicker control. Meeks adds that these are not DYI products and should therefore be administered by a professional.

In extreme cases, he says, fogging may be necessary to control the adults and allow time for standard sanitation efforts to control the population. He is also quick to point out that “fogging and pesticides are never the solution. There has to be an agreement between establishment owner and pest management professional that the former will maintain sanitary practices, and the latter will provide appropriate efforts when needed.”

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