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Little Fruit Flies, Big Problems
by John Barcay, PhD
It only takes an area the size of a person’s thumb to produce thousands and thousands of fruit flies. One adult female fruit fly can lay 15 to 20 eggs in a batch and as many as 500 batches in her two-week life cycle. A few fruit flies can quickly multiply into an infestation.
Example: Because 60 percent of the food service customers of Ecolab, a provider of cleaning, food safety and health protection products and services, report repetitive or ongoing issues with fruit flies, it is clear that these tiny insects are a persistent pest.
More Than an Annoyance
Although fruit flies don’t bite and have never been directly linked to foodborne illness they may be more than an annoyance. Because they travel between filthy breeding sites like mops or recycling bins to food or food-handling surfaces, they could potentially transport pathogenic contamination between areas.
Fruit flies can also pose a potential risk to a business’ reputation. Angry customers who encounter fruit flies may demand compensation for their meals, and health inspectors could give your sanitation audits failing marks due to a fruit fly infestation.
One species of fruit fly common in food-service areas is Drosophila melanogaster. The tiny, red-eyed fly, has been an especially annoying pest for many years and usually breeds in the bar area and recycling bins. Since the late 1990s, however, newer species of fruit flies have emerged, including Drosophila repleta. Drosophila repleta are larger (up to 1/4-inch long) and capable of congregating and breeding anywhere there is moisture and a buildup of decaying organic matter. Some common locations where fruit flies breed:
- On kitchen floors where stagnant water is allowed to sit for a week or longer;
- In drains;
- In the bottom of trash cans;
- In soft drink dispensing equipment;
- In espresso machines; and
- In garbage disposal units.
Sometimes these breeding locations are well hidden; behind walls, where seepage of water in the kitchen floor has degraded wallboard, or in ceilings where there’s condensation. These flies can even breed in small areas where standing, stagnant water has seeped under a table leg, a locker or a heavy piece of equipment.
The presence of fruit flies indicates that something somewhere is rotten.
The key to eliminating fruit flies is finding that location, cleaning it and removing the source. It’s not as simple as just spraying a pesticide, which isn’t effective unless the breeding source is also treated directly or removed through good sanitation practices.
Sanitation Key for Eradication
The best long-term way to prevent fruit fly infestations is to maintain good sanitation, targeting potential breeding sites. The only permanent way to eradicate fruit flies is to remove existing and potential breeding sources with thorough cleaning. Ongoing and consistent training of kitchen personnel on proper cleaning and sanitation is a must. Some areas are commonly missed, so kitchen personnel should practice checking for food debris under food lines and bar areas and watch for any accumulation of grime on floors – especially in the corners.
Drain lines from beverage dispensers, ice machines or espresso machines also must be flushed and cleaned weekly, and floor drains should be cleaned weekly. Comprehensive floor sanitation involves using a scrub brush with hot, soapy water (and a little elbow grease) rather than a pressure washer, which can degrade grout and blast food debris into hidden nooks and crannies. Power cleaning can actually make the situation worse. If kitchen staff uses power cleaning equipment, train them well on how to do so effectively and safely.
Besides cleaning measures, structural changes can make an area less prone to fruit fly infestation. Bars may need reconstruction if any portions are rotting from contact with spilled liquids or if fluids such as beer or soda are seeping into inaccessible voids. Walls near sinks may need replacing if they are breaking down from humidity or water. Keep floors in good condition – especially at the edges – to prevent moisture from getting behind walls. Tile grout – especially if cracked or crumbling – must be repaired.
Equipment such as garbage disposals, beverage dispensers, dough machines and even ice machines must be periodically opened by qualified staff and thoroughly cleaned of food debris and potential breeding material.
Keeping facilities free of fruit flies will always be an ongoing challenge. It is may be impossible to prevent fruit flies from entering your facility, but with proper sanitation, ongoing maintenance and treatment by a well-trained pest control professional, you can prevent them from breeding and multiplying.
John Barcay is a senior scientist for Pest Elimination at Ecolab Inc. (St. Paul, Minn.). Reach him at firstname.lastname@example.org.