It seems that when food contamination is considered, cockroaches and mice are the first things to crawl into one’s consciousness.

Those who have gone through food safety training know what flies do as soon as they land on food; they regurgitate. It’s not pretty but it’s true. If that fly has just come from outside and there are dogs in the neighborhood, one can only imagine what is coming up from the fly’s stomach only to land on the uncovered donut, cutting board or freshly cut lime.

I’ve heard it said by professionals that if they were forced to eat in an infested facility, they would prefer to eat in a place infested with roaches rather than flies. This should put a fly’s contamination threat in perspective.

There are several things that can be done to protect against flies, and you should adapt your strategy to fit the species. Small flies such as fruit flies, moth flies, phorid flies and fungus gnats are almost as common in food facilities as the common housefly. For today’s purposes, we’ll focus on the housefly and keeping them out of your facility is the best place to start. Make sure all windows are protected by screens and that all screens are in good shape. Does a screen door protect the receiving door? If so, an air door, which blows air out a door when it is open, is a very good tool. Just be aware that air doors can be quite expensive and must be installed correctly.

I’ve visited several kitchens where the air door isn’t working properly, only to discover that the air stream was misdirected to actually blow air flies into the kitchen. To see if an air door is working, simply hold a strip of ribbon in front of the airflow and then adjust the vents.

Fans are also good tools, as houseflies tend to shy away from moving air. They can be used to keep flies away from food being served outdoors, and, in some instances, can also protect salad bars.

If a screen door is impractical for your backdoor, there is a product called “Easy Screen,” which allows two overlapping, weighted screen panels to snap and unsnap. These are designed so that servers and delivery people can walk through while carrying things or wheeling in a hand truck.

One thing commonly heard among restaurant owners is, “My staff never props the back door open but, every time I visit, the door is open to either ‘bring in fresh air’ or let the smokers in and out.”  

Recognizing that the open door is a problem, it makes sense to move dumpsters as far away from receiving doors as is practical. Scattering fly bait granules around the dumpster will also help control the outdoor population.

Other tools to eliminate bugs include insect light traps or ILTs, which are effective in eliminating houseflies. There are two kinds of ILT. Electrocutors are traps that lure flying insects in and then electrocute them, but should never be used in a food facility. Sticky traps are used in foodservice. Both types use ultraviolet (ULV) light to attract flies to the traps and it is very important to replace ULV bulbs annually as they lose 7 percent of their ultraviolet qualities per month and, at the end of a season, are probably not attracting flies anymore.

Placement of ILTs is crucial for effectiveness. Industry research shows that a fly’s primary area of flight is three to six feet off the floor. Therefore, ILTs must be installed at the same height. Do not place sticky models over food or food surfaces as fly parts can fall when glue boards are being changed. Equally important, make sure ILTs are not visible from an outside door as this will attract flies when doors are opened.

As with any pest, denying flies food, moisture, and harborage is one step in a good pest management program.

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