Small fly infestations can be very challenging for business owners since they breed inside the account and can multiply quickly with their short life cycle. Customers won’t take kindly to bugs flying around the areas where their food is being prepared or their drinks are being dispensed. Health inspectors will have a problem with the presence of these pests, and employees won’t want to work in an environment where they’re swatting at flies all day. Properly identifying these pesky insects and their breeding sites, and implementing control methods including sanitation, physical and mechanical measures, and insecticide use is needed to keep your client’s space free of small flies.

Small Flies

Small flies can be problematic in commercial kitchens, food and beverage service areas, food-processing facilities, health facilities, and medical facilities. While they are a nuisance, small flies can also carry pathogens from breeding sites to food and food preparation areas. These pests multiply quickly when breeding sites and food sources are available. There are three common small flies that your clients are likely to encounter: fruit flies, phorid flies, and drain flies.

Fruit Flies

The first fly on the list is the fruit fly, and there are two species that can be problematic. The red-eyed fruit fly is about 1/8″ in length. It has a tan body with black rings across its abdomen. As their name suggests, these flies have red eyes. Dark-eyed fruit flies, as you may have guessed, have darker eyes. They look like red-eyed fruit flies but are bigger and darker. These pests can multiple very quickly.

Fruit flies lay eggs and feed on ripened, rotting, or decaying fruits and vegetables. Fermented items, like beer and wine, can also attract fruit flies. You are likely to find these flies in areas with food waste or moisture. Drains, mop buckets, garbage disposals, and trash bins are potential breeding spots for fruit flies. Dark-eyed fruit flies are typically more attracted to an advanced state of rot compared to red-eyed fruit flies.

Phorid Flies

Next up is the phorid fly. These flies have an arched thorax, so they are sometimes referred to as humpback flies. They move erratically across surfaces, which is why they can also be called scuttle flies. Phorid flies range in size from 1/64″ to 1/8″ and are black, brown, or yellowish. They can be mistaken for fruit flies and gnats.

Phorid flies prefer to breed in areas where moist organic matter has accumulated for five or more days. This often includes drains, recycle bins, trash bins, garbage disposals, and grease traps. Rotting food and decaying carcasses can also attract these flies. Chronic moisture, like from a drain leak, is often the reason behind phorid flies’ arrival. Cracked sewer or drain lines can cause large numbers of phorid flies to gather in the soil around the line.

Drain Flies

Drain flies are fuzzy with a moth-like appearance. This is why you may hear them referred to as moth flies. They have a brownish-grey body with lighter-colored wings. They range in size from 1/16″ to 1/4″. These pests can be sluggish and aren’t the best fliers. They have a jerky, irregular flight pattern. Drain flies are most active at night.

Like other small flies, drain flies prefer moist organic environments. If water has accumulated in a spot for more than a week, there’s a good chance drain flies will find it. Larvae live in drains where biofilm, a scum produced by bacteria, is present. These flies are often attracted to drain pans, infrequently used toilets, and areas where water collects including behind loose or broken tiles.

How to Control Small Flies

To manage small flies, the focus needs to be on eliminating their breeding sites and applying insecticides that will control populations, targeting both adults and larvae. As with any effective IPM program, the use of insecticides should only come after the small fly infestation has been correctly identified, the source of the problem has been found through the monitoring and inspection process, and the conducive conditions contributing to the problem have been determined and eliminated. Check out our three-step guide to manage a small fly infestation.

1. Indentify Pests & Breeding Sites

The first two things you need to do is properly identify the small fly species on site, and then inspect the area for conditions that could support small flies as well as other pests. Since small flies are attracted to moisture and organic matter, you’ll want to focus on areas where these could be present.

Common breeding sites include:

• Decaying fruits and vegetables
• Cracks, crevices, and areas where food and moisture collect
• Drains
• Dirty mops and brooms
• Beer and soda overflow trays and the outside of beverage lines
• Ice machines
• Leaky pipes
• Recycling bins
• Sources of stagnant water
• Trash bins

2. Eliminate Conducive Conditions

Once you have identified breeding sites, you’ll want to work with your client to eliminate favorable conditions that support larval development through both sanitation and physical or mechanical measures. This involves your client rolling up their sleeves, cleaning, and minimizing attractants. If small flies can’t find anything to eat or a place to breed, they won’t have a reason to stay. Small amounts of organic debris could attract and support these pests. Encourage your clients to get involved by:

• Cleaning up food and drinks spills promptly
• Cleaning soda fountain and beer tap drip trays
• Cleaning the areas where food residue can accumulate
• Eliminating standing water and repairing plumbing and sewage line leaks
• Examining produce to ensure fruit flies aren’t present and storing it in sealed bins in a cool storage area
• Keeping mops and buckets clean and hanging mops to dry
• Regularly cleaning drains. It’s best to do this at least two times a week to eliminate organic residues.
• Rinsing containers before placing them in the recycling bin
• Placing trash bins, recycling bins, and dumpsters away from entrances when possible
• Sealing cracks and crevices, repairing damaged tiles and kitchen fixtures or equipment to eliminate potential breeding sites
• Using drain baskets or filters to capture organic material that might clog drains, and emptying these daily.
• Using non-toxic fruit fly traps to capture adult fruit flies.

We know good sanitation and eliminating conducive conditions is key to preventing a small fly infestation. When dealing with organic build-up and chronic moisture conditions, bio sanitation is the most effective solution. This is the use of microbial surface and drain cleaners. The microbes actually digest the organic debris. Check out the InVade Bio Sanitation product line and technical guide to see how easy it is to utilize these probiotic cleaning products in a commercial kitchen environment and how easy it is to pursue a bio sanitation service business with confidence!

3. Treatment Applications

After properly identifying the small fly problem, inspecting and locating their breeding areas, and eliminating and preventing the conducive conditions, it’s time to proceed with the pesticide application. Treating your client’s space with pesticides will help to control current small fly populations including their larvae. Pesticide applications need to work in tandem with proper sanitation efforts. Relief from pesticides will be temporary if conducive conditions aren’t removed. Small flies will be more than happy to show up again if breeding sites and food sources return. Rockwell Labs offers a variety of products to help target small flies with most being classified as Green Zone products. These are products Rockwell considers to be suitable for green service programs.  

• BorActin: BorActin is a 99% boric acid, non-repellent powder that can be applied as a dust, spray, or foam. It can be used to treat organic build-up by poisoning the food sources of small flies, essentially turning the scum into bait. BorActin can be used in food areas when the facility is in operation, except in service areas. When used as a dust, apply at a rate of 1 lb per 1,000 sq ft. To kill adults and larvae, apply to organic build-up. For treatment of floor drains, apply up to 1 oz. If applying BorActin as a liquid, mix 1 cup by volume per gallon of water. You can mop or spray floors and non-food contact surfaces. BorActin is also very effective for controlling roaches by turning their food source, the organic debris, into bait as well.
• EcoVia IB: Our innovative EcoVia IB Bloks are formulated with botanical insecticide oils. The EcoVia IB Bloks kill small flies in small enclosed spaces. They also emit botanical vapors that repel small flies and other insects from an area. Their effectiveness is enhanced when they slowly dissolve in water like when they are placed in beverage fountain drip trays or set on drains. EcoVia IB Bloks are EPA 25(b) Exempt.
• InVite Lures: Our InVite Liquid Lure is a concentrated non-pesticidal attractant. It can be added to traps to help attract and capture small flies. For fruit flies, our non-toxic InVite Fruit Fly Lure is designed for small flies and can be applied to an insect glue board to help capture small flies. Our InVite Fruit Fly Traps are non-pesticidal traps for small flies that are ideal for use in food areas.
• OutLAST Pro: If you’re looking for a product to improve coverage and contact time, our OutLAST Pro foaming agent can help. It is long-lasting and has a broad-use label. It can be combined with BorActin, or other insecticides and bio sanitation products, to create thick, longer-lasting foam that retains liquid and is ideal for use in drains and wall voids.

Small flies can be quite worrisome for business owners, their customers, and their employees. An effective IPM program that includes the cooperation of facility management to identify and address any sites or conditions that could support flies is key to eliminating a current small fly infestation and preventing small flies from returning. Check out and download our Smally Fly Management technical guide.