[Annual Fly Control Issue] Beating Small Flies Requires Partnership

Features - Annual Fly Control Issue

Tackling a small fly infestation can be difficult. By building a strong partnership with your customers and working closely with them to implement the proper preventive actions and treatment techniques, you can help maintain a fly-free facility.


When it comes to the need for small fly management, customers may not always understand how important these programs are to their business. One of the most basic questions that must be answered is this: “Why does my facility need a small fly control program?” Frequently, the PMP is called upon to identify the importance of small fly management. Therefore, it’s important to understand that:

  • Small flies can be one of the primary carriers of disease organisms and can contaminate food and food preparation surfaces.
  • Small flies are often responsible for dissatisfied customers, distracted employees and health department violations, resulting in lost business, citations and employee complaints.
  • Small flies are prolific breeders capable of quickly spreading throughout a facility. They must be eliminated by using a multi-faceted approach. Generally, no single service, piece of equipment or inspection will eliminate small flies.
  • Fly control requires a pooling of resources, proactive partnering and continued technician follow-up until the flies and development sites are eliminated. In fact, the facility manager and PMP must understand that success depends upon identifying and removing all sites and conditions that support small fly development.

Sites of Small Flies.
Four flies to look for during service visits are fruit flies, fungus gnats, phorid flies and moth flies. Here are a few identification characteristics and commonly encountered developmental areas to inspect:

Fruit Flies (Drosophila spp.). Many fruit flies, though not all, have red eyes, a tan colored head and thorax, with a slightly darker, striped abdomen. They range in size from one-tenth to one-fifth of an inch long. Larvae are dirty white and maggot-shaped. Fruit flies can lay eggs and develop in almost any kind of moist, decaying organic material. The following is a partial list of common potential developmental sites:

  • Tiled areas with broken grout
  • Dirty mops and mop pails
  • Sour rags and towels
  • Food and drink preparation/storage areas
  • Cracks and voids
  • Trash receptacles, recycling containers and refuse disposal areas
  • Rubber mats
  • Under appliances and drip pans under refrigerators
  • Garbage disposals, dishwashers
  • Floor drains
  • Elevator pits
  • Near spilled food under equipment

Fungus Gnats. Adult fungus gnats are about one-sixteenth of an inch long. They are grayish to black in color, slender and appear mosquito-like with long legs and antennae. Larvae feed on fungus growing in the soil and moist organic matter. Common developmental sites include:

  • Areas of moisture and organic matter such as moist soil
  • Potted plants
  • Wet sub-roofing, particularly on flat roofs
  • Leaking pipes above ceilings/behind walls

Moth Flies (Psychodidae). The moth fly is about one-eighth of an inch long, with a dark gray body and lighter colored wings. The body and wings are densely covered with tiny hairs, which give the body a fuzzy appearance. Because polluted waters and wet organic materials are preferred developmental sites, inspect the following areas:

  • Broken drain pipes under the floor
  • Sump pump pits
  • Garbage cans
  • Clogged storm drains
  • Moist compost and decaying organic material
  • Sewer leaks/backups and septic tanks
  • Sinks and drains, particularly bathroom drains
  • Cracked shower pans, old decaying grout
  • Leaks under dishwashers and other equipment

Phorid Flies (Phoridae; humped back flies). Adult phorid flies are one-sixteenth to one-eighth of an inch long, with a humped back and yellowish-brown body (thorax). They are often confused with fruit flies, but lack the red eyes. In addition, the wing veins are few and have a simple pattern when compared to other small flies. When disturbed, phorid flies tend to run on surfaces rather than immediately fly away. Commonly encountered developmental locations are:

  • Broken sewer pipes
  • Garbage disposals, trash containers and compactors
  • Open or dry drains
  • Moist areas under commodes, tiles and kitchen equipment
  • Infrequently cleaned animal cages

Building a Partnership. Once you have located all potential and actual breeding and harborage sites, document them and communicate with the facility manager about what needs to be done to eliminate the small flies. Failure to remedy the problem often occurs with an incomplete inspection. Don’t stop when you find one source — small fly populations may be coming from multiple sources. Remember, while there are many steps the pest management professional can complete, day-to-day maintenance and sanitation is best handled by the facility. Preventing and controlling infestations requires a solid effort from both parties.

The first step in getting your customer on board is education. The customer needs to understand the components of your fly control program and have a basic knowledge of problematic small flies. Offer to host a training session and provide educational materials such as check lists and tip sheets. One of the key educational points is this: “If it is dry, they will die!”

Additionally, establish a pest sighting protocol. Early detection by the customer can be the difference between a small population and large infestation. A pest sighting protocol ensures that pests are reported in a timely manner, properly identified and serviced quickly and efficiently.

It’s also important to establish a clear understanding of roles and responsibilities. A lack of defined roles from each party can create ineffectiveness and finger pointing. One of the worst things that can happen to a PMP is to hear the customer say, “These are your flies — you take care of them!” Your customer should be responsible for the following actions:

  • Make the premises available and prepare for service in accordance with the service agreement and your recommendations.
  • Promptly correct sanitation and structural deficiencies that are noted on service reports.
  • With the pest management professional’s assistance, train their staff to conduct detailed, routine cleaning and drying, plus inspect their work to ensure they are doing what is required.

Control Methods.
Small fly problems are often caused by structural issues (i.e., improperly sloping floors, cracked tile areas, improperly sealed coves, etc.) or sanitation-related problems. Both structural and sanitation issues require complete cooperation from the client.

Sanitation. Small flies are dependent upon moisture and organic debris to breed and develop. Sanitation is critical to the success of any small fly control program. The PMP can accomplish more when requiring the facility manager or designee to accompany them on the inspection. Remediation of sites conducive to small fly population development is more likely when seen in person, rather than simply described on a report. Some common sanitation recommendations include:

  • Cover trash cans with sealed lids, use liners and empty trash cans frequently.
  • Clean Dumpsters and Dumpster pads weekly during fly season. Position Dumpsters as far away from the building as practical.
  • Rags and towels should be sealed in bags until cleaned and mops and brooms should be dry and clean.
  • Use an organic, enzymatic cleaner to eliminate residues and food debris in and around drains.
  • Use brushes to remove food debris in drains, on floors, under equipment and in grout areas.
  • Store produce in coolers and remove all rotting produce.
  • Clean spills immediately.
  • Use directed floor fans to help areas dry.

Exclusion/Mechanical. Flies can gain access to facilities through doors, windows and other openings. Conduct an inspection to determine whether exclusionary measures are adequate to prevent flies from entering the facility. It may be necessary to replace window or door screening with size 20 mesh screens. Check for air flow (positive or negative pressure) in the building. If the fly source is outdoors, does opening the doors draw insects into the building? The facility manager may need to seal around windows and doors and place air curtains above “high-traffic” entrances. Caulking of cracks and gaps also is important to prevent access to small flies to moist areas containing organic matter.

Traps. Insect light traps are useful for ongoing control of phorid flies and fungus gnats. Specific small fly traps, such as those for fruit flies that contain grenadine or vinegar, can help reduce fly numbers. Be certain to inspect and replace these traps so the bait does not become rancid, supporting fly development. Hanging glue traps can be used to lower fly populations if non-chemical control is needed.


Phil Pierce is the technical services manager and entomologist at Western Pest Services, Parsippany, N.J. Bob Johnson is a technical specialist and entomologist at the same firm. Learn more about Western by visiting www.westernpest.com.