Small Flies are Big Pests

Small flies can cause big problems. In fact, two species — fruit flies and drain/moth flies — tied for generating the largest percentage of service calls (37 percent) and for being the most problematic (75 percent) in the past year, according to pest management professionals who participated in the 2023 PCT State of the Small Fly Control Market survey, sponsored by Nisus.

Adam Woodard, technical director, J&J Exterminating, Lafayette, La., said red-eyed and dark-eyed fruit flies were common culprits in his market.

“Those are probably the most challenging because you’ve really got to find the source and sometimes it’s not obvious where it is. You just have to do a little bit of investigating and thinking outside the box to try to find where they’re at,” he said.

Fruit flies can breed just about anywhere: rotting produce, fermenting spills and residues, underneath tiles, in drains, garbage disposals, waste bins, mop buckets, and gaps and voids where trapped food debris is decaying.

At Spidexx Pest Control, drain/moth flies are the number one small-fly complaint of residential customers. The flies breed in sewer and plumbing systems and commonly enter homes when the water seals in unused drains evaporate, said Nate Heider, the company’s regional manager in Minneapolis, Minn.

Running water in the drain usually solves the problem, but finding the problem drain can be difficult, especially when it’s under the carpeting of a finished basement, he said.

Heider also sees fungus gnat problems at the homes of people who have overwatered the houseplants. In recent years, the popularity of houseplants, especially among millennials, has soared, reported PCT sister publication Garden Center magazine.

Fungus gnats accounted for 12 percent of small fly service calls in the past year and were problematic for 55 percent of PMPs, found the PCT survey.

“It’s surprising sometimes how little you have to overwater those plants. You get a little bit of mold or fungus that forms underneath the topsoil and all of a sudden, you’ve got fungal gnats,” said Heider.

Phorid flies were problematic for 44 percent of PMPs and made up 11 percent of small-fly related service calls.

“The phorid flies sometimes can be challenging because they may be associated with a sub-slab sewer leak,” said Woodard.

For Purcor Pest Solutions, which operates in six states, the phorid, or “humpback” fly, is the most difficult to control in commercial kitchens because “they will breed in and infest anything,” said David Joles, the company’s East market vice president. They’ll get under tile and mortar, in wall voids, and populations develop quickly, he explained.

Summer was the busiest season for small fly control service calls, reported 49 percent of PMPs in the PCT survey.

Restaurants and bars are busy in summer, as well, which contributes to small fly infestations. In warm weather, spilled food and beverages quickly ferment and decay, and over-worked kitchen crews have less time to prioritize cleaning and sanitation, said PMPs in follow-up interviews.

Small flies pose a risk to public health as they move between breeding sites in decay and sewage to glasses, dishes and food prep surfaces. “They can transfer bacteria from one place to another, just like large flies or cockroaches,” said Ryan Gates, technical services manager, Versacor, Southlake, Texas.

Thirty-five percent of PMPs said the number of small fly jobs at their company locations increased in 2022 from the year before, while 52 percent said the number of calls remained the same.

Small flies are one of the most difficult pests to control in commercial accounts, said Joles. “Those small flies are the hardest thing we do. German cockroaches, honestly, they’re fairly easy to control,” he said.