Fruit Flies

Everything You Always Wanted to Know… But Were Afraid to Ask

Fruit flies, or as they are more properly known small vinegar flies, have become a major nuisance in restaurants, bars, grocery stores, bakeries, fruit markets, and offices. Heavy populations of these pests can develop from a single source. The Red-Eyed Fruit Fly is pale brown in color with bright red eyes. The adults are poor fliers and they prefer fruits and vegetables that are in the earliest stage of decomposition. The Dark-Eyed Fruit Fly appears blackish brown with dark red eyes. It is slightly larger than the red eyed fruit fly, tends to be a strong flier, and prefers late stage decomposition. The larvae are found burrowed deep into moist, smelly organic debris.

How Do They Get In?

Fruit flies live naturally outdoors during the warmer months and are attracted indoors by food odors, garbage containers, and compactors. They can easily fly in through an open door or various life stages may be brought in on fruit and vegetable deliveries. Even fruits and vegetables in employee lunches can carry these flies.
Where do they breed?

Female flies search out micro environments containing moist, fermenting organic debris and may lay 500 eggs (about 30 a day during their life span) on the surface of this material. Here are some favorite locations: the accumulated sludge that sticks to the bottom of garbage cans, the “gelatinous scum” that builds up inside of floor drains, the rotten piece of fruit or vegetable that is stuck on the floor under a work table, the loose floor tiles under the dishwasher or sink, the dirty mop that is stuck in a closet, and the drain pan under a refrigerator.

What Is Their Life Cycle and Development?

The eggs hatch in about 24 hours into tiny larvae that feed near the surface of the fermenting food. After five to six days they crawl to drier areas to pupate. Several days later new flies emerge and are attracted to light where they mate and then resume the process of laying more eggs. With temperatures in the mid to upper 70’s the whole process takes 8 to 10 days. Under cooler conditions it may take 18 to 21 days to complete the life cycle.

Fruit Fly Life Cycle

Do They Bite?

No, fruit flies do not bite humans. They do not have biting mouthparts. They can be quite a nuisance as they hover around in search of suitable breeding sites.

How Do You Get Rid of Them?

The key to control is to locate and eliminate the breeding sites. Improved sanitation and maintenance and the elimination of excess moisture are also critical steps to eliminate fruit flies. There are no magic sprays to solve the problem. This is a hands and knees job to pull out and remove the moist organic debris from under work tables and counters. The accumulated scum inside floor drains needs to be removed. Loose and broken floor tiles and coving must be repaired. Moisture and standing water must not be allowed to accumulate overnight. Aerosol mists or fogs containing pyrethrins will give good kill of the adult flies but will do nothing to eliminate or control the eggs and larvae that are located in the breeding sites. The results will be temporary at best. Repeated treatments with these aerosols will be needed to keep killing the newly emerging adults flies until the breeding sites are found and eliminated. Ultra violet insect light traps (ILT’s) are of little help because fruit flies are more attracted to odor than to the ultra violet light. Pouring bleach into a drain will not work either. Bleach is a good disinfectant and sanitizer but will not dissolve the greasy organic material stuck inside a floor drain.

What Other Control Methods are Available?

Recent research has shown that any of the biological products such as BioZyme, InVade, BioGel (containing .good bacteria) applied as a foam do a good job of digesting and removing the organic scum in cracks, crevices, under warped tiles, and in floor drains. Well placed bottle traps containing an effective attractant will capture adult fruit flies. However, traps by themselves will not solve fruit fly problems. The breeding sites must be found and eliminated!

How Do You Find and Eliminate the,
Breeding Site(s)?

Remember the basic biology. Fruit flies need moisture, rotting organic debris, and a little warmth. Search for and eliminate these conditions.

• Remove the liner and inspect the bottom of rubbish containers. Scrape and scrub out the debris that accumulates at the bottom of the container. Make sure they are dry before replacing the trash bag liner.
• Look where empty pop cans are stored for recycling. If the cans stay around too long, the small amounts of pop or juice left inside becomes a breeding site.
• Find where used coffee grounds are put and make sure the area is cleaned every day.

• Inspect under every food preparation counter or table. Remove food and debris that is trapped behind rear table legs or wedged against the wall.
• Open up floor drains to brush and scrape out the accumulated debris. You may need to use a degreasing solvent and a stiff brush to loosen the material. Very hot water or a low pressure steam cleaner may be used to loosen up the debris and scum and clean the inside of the drain. Do not pour bleach down the drain. It will not solve the problem.
• Inspect beverage systems. Clean the rubber cup that holds the beverage dispenser gun. Follow the lines to the drain. Look for and remove accumulated pop scum and clean the floor drains.
• All exposed fruits and vegetables not consumed immediately should be refrigerated. Cool storage slows the insect development. Inspect displays and discard damaged or rotting fruits and vegetables.
• Look for standing water under ice machines and around floor drains. Correct these conditions. Just a tiny bit of food kicked under the ice machine onto a wet floor can become a potent breeding site.
• Repair loose, missing, or damaged floor tiles in areas where moisture and food debris accumulates. This usually occurs under dishwashers and around stoves and ovens.
• Make sure mops are hung properly and allowed to dry completely. Fruit flies can breed in the food that accumulates in the top of the mop head.
• Keep doors and windows closed or make sure that fine mesh screen doors are installed and operating properly.
• Use a wet/dry vacuum to mechanically remove standing water in corners, under equipment or from “low spots” on the floor. Place a fan down low on the floor to dry out areas after the cleanup is completed.