The why of the fly

Like most small fly species, fruit flies (Drosophilidae) aren’t terribly picky about where they gather and multiply. (PHOTO: ARLINDO71/E+/GETTY IMAGES)

Like most small fly species, fruit flies (Drosophilidae) aren’t terribly picky about where they gather and multiply. (PHOTO: ARLINDO71/E+/GETTY IMAGES)

QUESTION:  Dan, I am having intermittent small fly issues at a restaurant. In trying to work with the client, I find that I am not as successful at getting their help as I would like. What can I tell them to get better cooperation?
—Buzz Ablassen

ANSWER: Buzz, the position you must take is that pest prevention services are a public health function and a food safety function. In that light, the most important task is to discover the source of the fly problem. Remember the core function pest management professionals (PMPs) serve: We help maintain a pest-free environment for our clients.

Starting from the position that every service should include a structural, sanitation and storage inspection, you must look for likely breeding areas and food sources. By proactively seeking out conducive conditions and entry points, you are more likely to prevent an introduction from becoming an infestation, or a burgeoning problem from becoming a full-blown crisis.

You must answer the question of why the flies are there in the first place. In the case of small flies, it usually means there are structural defects, or sanitation problems inside the building — although it is possible for any of the small fly species to come in from outside. This holds true even if you find one fly; you must still investigate thoroughly to make sure you are not catching the problem at the beginning.

If the problem is decaying fruits or vegetables, dispose of the decaying food and advise the client on cleaning up the area and monitoring their stock in the future.

Likewise, with fungus gnats (Sciaridae) found in overwatered or otherwise neglected plants, advise the client to remove the plants and water more appropriately in the future.

Drain flies (Psychodidae) and other filth fly species can be a bit trickier to address. There are several chemical and biological supplements to maintain clean and functional drains, but always start by removing the organic material that is supporting the infestation. Remember to wear proper personal protective equipment (PPE) when working with drains. The organic material being removed may contain microorganisms that could be harmful if inhaled, ingested or get in your eyes.

In some cases, the work is beyond the skill set of the average pest management professional. Plumbing and flooring defects typically require other tradespeople who are trained and skilled in finding and fixing problems. Do not overpromise and underdeliver. Assess the situation, and if the problem is appropriately handled by another trade, document the recommendation and communicate that to the client.

As a reminder:

  • Exercise your intellectual curiosity and look for all the places flies may gain entry, hide, feed and breed. If you don’t find the entry points, harborage or food source easily, keep looking until you do. If flies are in the building, it’s a structural, sanitation or entry problem.
  • Find, document and communicate any conducive conditions that must be addressed.
  • Clearly define client expectations and your action plan, and the expectations for client action.
  • Keep following up on a schedule that makes sense for the level of the problem and the setting.

Read moreMoisture is the common denominator in small fly sources

Email your questions about insect identification and pest management technologies to Your questions most likely will be printed and answered in one of Pest Management Professional’s upcoming columns.

About the Author

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Baldwin is the vice president of technical services for Hawx Pest Control in Tombstone, Ariz. He is also an Editorial Advisory Board member for PMP. He can be reached at

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