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Fruit Flies

Fruit Fly

Overview

There are over 4,500 species of fruit flies in the world. The genus Drosophila includes a large number of species of fruit flies belonging to the family Drosophilidae. Among these species, D. melanogaster Meigen, D. repleta Wollaston, D. funebris (F.) and D. busckii are considered the most common species of fruit flies found inside buildings.

Although these flies are attracted to ripened or fermenting fruits and vegetables, they can breed in drains and wherever moist organic matter gathers. This makes them more than nuisance year round, especially where sanitation is an issue. Therefore, the key to successful fruit fly management program should involve the establishment of partnership between the location's sanitation personnel and the pest management professional (PMP) in charge in this facility.

Proactive approach is better. Start the fruit fly management program early before a big infestation is established in your place.

Identification

Red-eyed Fruit Flies

Adults are small flies about 1/8 inch long.
Adults with red eyes.
Have transverse black rings across their abdomen.
Larvae are yellowish white, small, legless and pointed at the head end with inconspicuous head.

Dark-eyed Fruit Flies

Adults are a little larger in appearance than red-eyed fruit flies with dark eyes.

Biology

Fruit flies multiply quickly. At 70°F and 85°F, life cycle can complete in two weeks and 8 days, respectively. A mated female can lay about 500 eggs in its lifetime. Eggs hatch in 24 hours and go through three larval instars within four to six days. Puparium (hardened exoskeleton of the last larval instar) and pupa stage lasts five to six days. Newly emerged flies are attracted to light. After 48 hours, become sexually active, mate and females lay eggs in moist fermenting matter.

Habits

Red-eyed Fruit Flies

Attracted to ripened, fermenting and decaying fruits and vegetables.
Larvae breed on various yeasts, which develop on organic matter that is relatively new or in mild decay.
Adults are strong fliers, traveling up to 6 miles in 24 hours.
Newly emerged flies are attracted to light.
Larvae feed on fermenting foods or any moist organic materials.

Dark-eyed Fruit Flies

Feed and breed in new and old decayed organic matter.
Adults sit on walls as well as around window and door sills in public areas near their breeding sources.
Can breed in hard to clean areas, such as broken tiles, broken baseboards, neglected floor drains and other similar areas.

Management

Long-term management will not be accomplished without these four steps: locating larva feeding areas, removing breeding areas, using pesticides, and prevent and exclude.

1. Inspection & Monitoring

Inspection

The early detection of any pest problems, including fruit flies will save time and efforts. In areas where fruit flies are common pests, apply a regular inspection to locate all larvae feeding and breeding places. Because fruit fly adults can easily follow air currents, they could have several breeding places inside a structure wherever fermenting, moist and decaying organic materials are available. Anyhow, during the inspection, pay particular attentions to the following common fruit fly breeding places:

Where fruits or vegetables are stored outside of refrigerators or coolers.
Recycling bins seldom used, emptied or cleaned.
Garbage cans, underneath and behind large appliances.
The film of debris that naturally accumulates in pipes, traps, sinks and drains.
Fermented dishwater from sinks, drain water from refrigerators or iceboxes.
Where the legs or feet of appliances, tables or cabinets touch the floor to locate any tiny amounts of organic debris that can harbor thousands of fly larvae.
Beneath counters and unseen boxes of stacked materials on a bottom shelf to locate rotting fruits and vegetables.
Empty tomato, ketchup, fruit and vegetable bottles stored in the basement.
Empty bottles or cans of vinegar, wine, cider and beer. Larvae feed on yeast of fermenting liquids.
Under floor mats.
All small cracks and crevices at floor level.
Dirty dried mops or brooms.
Cracks and voids behind liquor bars.
Any leaking pipe or standing water.
Outdoors, nearby dumpsters, garbage cans or in damp compost piles where fruits and vegetables are discarded.

Monitoring

Insect Light Traps (ILTs)

Use ILTs indoors to monitor newly emerged adult fruit flies. Although traps are used for monitoring purposes, one fertilized female trapped eliminate 500 fruit flies.
Do not place ILTs too close to the doorways where the flying insect may not recognize them. It is known that LTTs are most effective when they are placed within 15 to 20 feet of every exterior door and at 4-5 feet high.
Do NOT use ceiling mounted ILTs in food preparation areas.
Electric Grid ILT's should be mounted a minimum of 10 feet from any food preparation surface.
Adhesive ILT's should be mounted a minimum of three feet horizontally from any food preparation surface.

Food Attractant Traps

There are various commercially available fruit fly traps that use vinegar or other fermenting matter to lure and capture adult fruit flies. Baited jar traps are usually designed with special tops that allow access but discourage escape of fruit flies. To successfully use food attractant traps, apply the following practices:

Place the traps in areas where fruit fly activity is sighted or near potential breeding sites, such as behind or under bars, beverage centers, dishwashers, food displays, food service islands, sinks, ovens, supply racks, vending machines, food preparation tables, etc. These traps need to be marked on a map. During each service visit, the Pest Management Professional (PMP) should inspect each station and readjust the locations if needed.
Avoid areas where traps may be disturbed or tipped.
Do not place traps over food preparation or serving areas.
Make sure to dispose of traps when full of flies or after 30-days of use and replace with new traps.
Be aware of airflow dynamics of the facility. These air currents may blow fruit fly adults away from the traps.
Be aware that the traps capturing more flies than others are the closest to the breeding sources.
Use enough monitoring traps to cover all fruit fly breeding areas.

2.Removal of Breeding Areas

To stop the fruit fly breeding cycle and reduce odors, thoroughly clean up any fermenting items and organic matter. It is recommended to use a proven microbial product that eats away grease, food debris and other wastes (larvae food). Foaming bio-cleaning products are preferred forms for this work. They can reach and stick to hard- to-clean surfaces where larvae could be easily missed by using other cleaning forms. Invest enough time to bio-clean all possible larval breeding sources, including drains, under appliances, under floor mats, around plants, dumpsters, cracks and crevices, etc. Never use bleach or any types of boric acid dusts in these areas, as they will deter the bio-product being used in the cleaning. It is suggested to repeating applications at 2 to 4 week intervals depending upon the severity of infestation.

3.Pesticides

Pesticide treatments will provide only a temporary relief. Before treatment, make sure to remove decaying organic matter. If pesticide application is needed, your PMP will:
Use a proven residual insecticides and apply limited crack, crevices and spot treatments to the following areas:

Under appliances.
Under floor mats.
Around plants, dumpsters, cracks and crevices around ceramic tile, windows, doors and grout joints, etc.
Apply Ultra-Low Volume (ULV) or space treatments using aerosol generators to knockdown exposed adult fruit flies, especially in high infestations.
Repeat applications at 2 to 4 week intervals depending upon the severity of infestation.
Apply insect growth regulators (IGR) approved and labeled for drain treatments into and around the downspout and catch basin area, as applicable.

4.Prevention and Exclusion

If properly implemented, prevention and exclusion practices will help in keeping the fruit flies away or keep their number under control. The following are some recommendations for fruit fly prevention and exclusion:

Do not buy wounded fruits and vegetables (eggs or larvae could be present in the wounded area).
Ripened fruits and vegetables should be eaten, discarded or refrigerated.
Cut and discard damaged portions of fruits and vegetables.
Regularly sanitize and clean spilled food or fruit juice (pay particular attention to the back of a cabinet, under a refrigerator and floor cracks and crevices).
Regulatory empty and clean a recycling bin.
Store fruit, vegetable and organic materials in well sealed containers.
Screen windows, doors and openings with tight-fitting (16 mesh) screens.
Fans directed at boxes of fruits and vegetables will keep flies from landing and laying eggs as well as help dry out liquids.

FAQ

Q. I have many fruit flies hanging out in my house due to birds that I have with a lot of food and fruit available at all times. What should I do please help?
A. Properly ID the fly. Botanical pesticides with a pyrethrin-based formulation can be used carefully around birds. It will help to knockdown the population of adult flies, but removing the breeding and food sources is the only long-term response.

Q. My wife and I live in an old farm home in the countryside of the state of Minnesota. We have a very serious fly problem. At all times, we keep our house very clean and our garbage is kept in a closed container until it goes to the dump each week. I've tried different commercial fly's sprays and fly paper which both work temporarily. Within days we have hundreds of flies in our house, gathering mainly around windows, and they seem to be worse upstairs.
A. Properly ID the fly. To solve a fly problem you must eliminate the breeding source, which could be an organic source, or perhaps a dead rodent.
If this is an ongoing seasonal problem in your house, the breeding source is not inside your home, but outside. We recommend you to call your pest management professional to apply an exterior treatment to walls and entry openings using a proven residual pesticide. If this is a new problem, since your house is well cleaned and sanitized, you may have a dead rodent in the attic or in a wall. Carefully, inspect to remove and clean dead rodents in your house. If you can't remove the rodent, time will take care of the problem as it decays.

Q. I have continually seen fruit flies (red and black eyed), phorid flies and moth/darin flies in loading area, garbage collecting area, kitchen and storage areas. I need recommendations on how to battle these little buggers.

Keep garbage area clean, schedule more frequent garbage pick up, and remove clutter around dumpsters.
Use bio-cleaning products to help eliminating organic matters in and around garbage areas, vending machines, rarely moved appliances, and other areas i.e., in and around the kitchen drains.
In areas where fruit flies may gain access to operation and other sensitive places, install running fans to keep these areas dry and disturb their flying and movement patterns.
Readjust the ILTs locations and heights (see above under Insect Light Traps).
In garbage areas, keep lights shut off all the time, except when they are needed (motion lights can be an option).
Place fruit fly bait stations in all fruit fly breeding areas along with ILTs (see above under Food Attractant Traps).