Bakers Journal

Small-fly Zone

August 14, 2015
By Alice Sinia

Why small flies can cause big issues for bakeries

Small fly infestations typically cannot be resolved by only using insecticides. Photo: Orkin Canada

Don’t let their size fool you; small flies can be one of the biggest pest threats to bakeries. Attracted to the dough, yeast and moisture found inside, bakeries provide everything these pests need to survive and can be ideal breeding grounds if proper fly control is not maintained.

Small flies should be a concern for several reasons: they reproduce rapidly; they can contaminate food and damage your reputation; and they can be costly.

As a result, fly control is imperative. The best strategy for managing small flies is implementing an ongoing fly control program that utilizes integrated pest management (IPM) practices such as sanitation, facility maintenance and exclusion.

Here is a look at common small fly species that infest bakeries, and the steps that can be taken to help keep them away from your business.

Common Small Fly Species
Some of the most common small fly species to infest bakeries are drain flies, fruit flies and phorid flies.

Drain flies are about 2 to 4 millimetres long and often referred to as moth flies because they are covered with long fuzzy hairs. They breed in biofilm in drains or on the surface of moist, slimy decaying organic matter in drains, sewages or other similar moist environments – including under building slabs where broken pipes may be located. The developing larvae bury themselves into the film while breathing with respiratory tubes pushed through the surface of the film.

Need to know fact: While drain flies breed in raw sewage and other decaying organic matters, they are not known to transmit human diseases.

Fruit flies are a little bigger, with an average body length of 3 to 5 millimetres. They can be identified by their usually large, bright red eyes. Fruit flies are attracted to fermenting, sugary, organic matters and lay their eggs on or near fruits, vegetables and other decaying organic matter. They also thrive in fermented materials often found in floor drains and trash cans. The common fruit fly is known for its ability to reproduce rapidly – eggs can hatch within two days and new adults can be found after only eight days.

Need to know fact: If consumed, fruit fly larvae can cause stomach distress or illness.

Phorid flies are easily recognized by their humped backs and small head relative to body, although sometimes they are mistaken for gnats. They range in size from 1 to 4 millimetres long. Phorid flies flourish in thick, decaying organic material in drains, at the bottoms of moist trash containers, under kitchen equipment and in mop heads or over-watered potted plants.

Need to know fact: The phorid fly is known in some regions as the coffin fly because they are also fond of decaying flesh and capable of creating sustainable communities in coffins.

Control and Prevention
The most noticeable sign of any small fly infestation is the appearance of adult flies. If you suspect your facility has small flies, it’s important to contact a pest management professional for help. Small fly infestations can be extremely difficult to control and typically cannot be resolved by only using insecticides. Instead, it’s important to locate and eliminate the source of the infestation and conditions that support it.

Here are several IPM practices you can implement on a regular basis to help protect your bakery from small flies.

Fortify entrances
There are several steps you can take to ensure your entrances aren’t providing flies easy access to your bakery. First, remind employees to keep doors closed whenever they are not in use. Next, seal all doors and windows with weather stripping and correctly fitting door sweeps. Work with an HVAC professional to make sure you have positive airflow, meaning air flows out, not into your building when doors are open. You can add a second layer of protection by installing two sets of doors, which add an extra boundary line for flies to get through. Air curtains, or wall-mounted fans that create a wall of air pests can’t fly through, can also be installed at entrances.

Minimize odours
Odours are one of the key attractors for small flies. To keep odours to a minimum, line and regularly empty garbage cans and recycle bins, and be sure to remove wet garbage as often as possible. Keep exterior dumpsters as far away from the building as possible, and rotate dumpsters on a regular basis. Clean up any spills immediately and use a bacterial cleaner to dissolve organic material on drains and floors.

Don’t let your guard down
Continually be on the lookout for potential small fly breeding or feeding sites. Focus on dead-end spaces in machines, equipment footing and other hard-to-reach areas, and inspect all incoming shipments for signs of fly activity. Look for adult flies rather than eggs. Use a drain scope to check for pipe cracks. Remember, broken pipes can lead to moisture under building slabs, which can create an ideal breeding site. Monitor for fly activities using various fly traps in high fly-risk areas such as a yeast room or dough fermenting room.

Small-fly infestations can be difficult to control once established. Work with your pest management professional to develop a customized small fly control program to help minimize conducive conditions and attractors, and keep these pests from negatively affecting business.

Alice Sinia, Ph.D., is a resident entomologist with Orkin Canada. She focuses on government regulations pertaining to the pest control industry. With more than 10 years of experience, she manages the quality assurance laboratory for Orkin Canada and performs analytical entomology as well as provides technical support in pest/insect identification to branch offices and clients. For more information, email her at or visit

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