No Time For Flies

— By Pat Hottel —

Controlling filth flies inside — and outside — restaurant facilities.


Filth flies, like house flies and bottle flies, reproduce quickly and are associated with pathogen laden environments like manure, garbage and sewage. The bodies are well adapted for transporting the microorganisms responsible for foodborne illnesses to our food and food contact surfaces. As summer months approach, a relatively quick life cycle from egg to adult becomes even shorter. Depending on the species, development can occur in as little as 1 week. As a result, we can see populations explode in the months of July, August and September. Their short life cycle and association with unsanitary conditions can place our facilities at risk for contamination.

How Can We Prevent Fly Issues?

Prevention should always be the first line defense in pest management. For filth flies, this means focusing on the exterior which is the primary area for fly development. This includes reducing fly attractants, eliminating exterior breeding sites and fly exclusion.

Key exterior fly prevention targets include:


  • Garbage Handling: Dumpster areas must be kept as clean and tidy as possible to reduce attractants and development sites. The dumpster pad should be cleaned regularly to remove food containers and food residues. Trash receptacles used for client food containers should have self-closing lids and be emptied at least daily. Self-closing lids not only reduce the ability for flies to access food, but it also reduce food odor attractants. The same is true for the dumpster area. Removing food residues and keeping dumpster lids closed can reduce general fly attractions. Fly baits or residual spray treatments applied by the pest management firm can be used to supplement good sanitation practices where needed.


  • Doors: A restaurant cannot keep doors closed all the time, but doors should never be propped open or left open longer than necessary for the movement of people and goods into and out of the building. Doors should also be well sealed when closed, including the base of the door. Flies don’t just fly into restaurants; they will enter from the bottom of the door via crawling. Door seals specifically designed for pest exclusion are recommended over standard weather-stripping devices. Rubber seals are preferred over brushes since they are easier to clean. Specially designed seals for the center of double doors are also available, called astragal seals. The vertical opening between double doors is often overlooked as a pest entry point. Xcluder is one manufacturer of a variety of pest-proofing door seals. Any door that is left open for ventilation purposes should be equipped with a tight-fitting screen.


  • Drive-Thru Windows: Just like doors, drive-thru windows should not be left open longer than necessary for customer service. Air curtains or a positive air flow can help prevent insect entry. Plexiglass has been used during the pandemic to help reduce COVID-19 exposure. The reduced window opening can also help reduce access by flies and should be considered as a permanent fixture even post pandemic. The smaller the opening, the less opportunity for insects to enter.


  • Outdoor Dining Areas: Flies can be attracted to food aromas emanating from exterior dining areas. Keeping these areas clean — and removing food, dishes and utensils promptly — are good practices. Use of ceiling fans can help in some situations to reduce the fly’s ability to navigate against air currents. Insecticide baits or treatment of fly resting spots near the dining area can be used as well.


Interior Defenses

Because the restaurant cannot be kept sealed 100% of the time and still serve customers, there is always the potential for some flies to enter. Good exclusion is helpful in reducing numbers but may not totally prevent all pest entry. Therefore, there should be some interior tools used to supplement the exterior efforts.

Strategically placed insect light traps are one tool that is used to intercept interior migrations of insects and to monitor for activity. Captures should be identified and counted each service and trends in activity analyzed. Further actions should be taken based on what the traps tell us. Insect light traps should be placed in identified paths of flies; however, they should not be placed where they might attract flies toward open food or food preparation surfaces. Flies can transport and shed foodborne illness during flight and/or if they rest on food. Light traps should not be located where they might draw insects toward the building from the exterior. This can occur if the light can be viewed from the exterior through a glass window or door. A light trap placed on an interior wall, facing a drive-thru window, may cause more insects to enter than are captured. It would not be considered a good placement.

Fans can also be used on the interior to keep flies away from key areas such as interior dining rooms or serving counters. Insecticides may be used to supplement other control methods when needed.





— Patricia Hottel is technical director at McCloud Services, a leader in integrated pest management, serving the food supply chain, retail industries and more, headquartered in South Elgin, Illinois.

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