NEW GARDEN TWP, PA — Phorid flies are swarming homes by the hundreds in a New Garden Township neighborhood, CBS Philadelphia reported, expanding a persistent problem for Chester County’s mushroom industry into a quality-of-life issue that has prompted residents to organize and document the infestation.
Residents of Heatherly Lane described tiny black insects invading kitchens and living areas and making it difficult to open windows. The flies, also known as scuttle flies, breed in compost used by mushroom farms.
“You can’t have a window open,” longtime homeowner Judy Stoltz told CBS Philadelphia. “They’re really a nuisance, but a real inconvenience, too.”
Her husband, John Stoltz, described the flies as a “definite problem” in comments to CBS Philadelphia, noting that they appeared relatively early this year and that he expects conditions to worsen as the season progresses.
The infestation has also spurred residents to organize. Homeowners created a Facebook group to exchange information and post photographs, including images of traps covered with phorid flies.
Michele Hanna, another New Garden homeowner, described to CBS Philadelphia how the insects have swarmed her kitchen and living room, at times flying around her face as she tried to watch television. She said she did not know phorid flies were a problem when she bought her house.
“Maybe one day, we’ll just have two come in the house,” Hanna told CBS Philadelphia. “Last year, I probably had 1,000 come in.”
The residential complaints add another dimension to a pest problem already affecting Chester County’s mushroom industry, which employs about 7,000 people. The Pennsylvania Department of Agriculture is closely monitoring phorid fly populations, according to CBS Philadelphia.
The American Mushroom Institute outlined several measures growers are taking to reduce fly populations, including upgrading seals around doors and vents, applying targeted chemical treatments, removing contaminated substrate and working with Penn State on control practices.
“Not all farms have flies,” Lori Harrison, the institute’s vice president of communications and industry relations, told CBS Philadelphia. She cited Penn State research finding that phorid flies can be dispersed by wind, making it impossible to connect flies at a particular location to a specific mushroom house.
The industry has also turned to specialized fly netting. According to the American Mushroom Institute, the U.S. Environmental Protection Agency approved emergency use of the netting for mushroom farms in fall 2025 after data indicated it could help control phorid flies.
The institute is also exploring pesticide products that could potentially be used in residential settings as homeowners continue looking for a lasting way to reduce the infestations.
Read the full CBS Philadelphia report at https://www.cbsnews.com/philadelphia/news/phorid-fly-infestation-kennett-mushroom-farms/
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