KENNETT SQUARE — There’s no getting around this pesky situation. In an effort to curb the presence of phorid flies, Pennsylvania is enhancing an ongoing quarantine in New Garden and Kennett by expanding the order to all mushroom growers in Chester County.
The phorid fly, an invasive pest, is responsible for destroying as much as 40% of the region’s mushroom crops each year while causing increased havoc inside the homes of local residents.
Wednesday, Pennsylvania Agriculture Secretary Russell Redding announced the Commonwealth has broadened its January 2025 quarantine to combat the phorid fly to better protect the Chester County’s most valuable crop: mushrooms.
A mushroom farm in New Garden Township is seen here. (Jen Samuel — Daily Local News)
Americans know Kennett Square as the Mushroom Capital of the World.
Southern Chester County’s mushroom farms, production houses and packaging facilities are densely located in New Garden and Kennett townships between the boroughs of Kennett Square and Avondale.
That’s the heart of the industry, and part of a 50-square-mile area that produces 60% of all mushrooms grown in North America.
The updated Pennsylvania Department of Agriculture order hopes to expand proactive efforts to control Phorid flies, also known as Megaselia halterata.
As the insect destroys nearly half of the annual crop grown in Southeastern Pennsylvania’s mushroom farms, there is a sense of urgency to turn the tide. And over recent years, the pest has become a major a nuisance area to homeowners and renters and small business owners.
Further, the Shapiro Administration made $1 million in state funds available through the Chester County Conservation District to support farmers in meeting new quarantine order requirements to control the pests. This is an increase of $500K compared to the amount offered in 2025.
Kennett Square Mayor Matthew Fetick expressed gratitude for Shapiro and Redding’s “concentrated effort” over the last year to “collaborate on long-term solutions regarding the phorid fly problem.”
The ongoing support for not only research but also for providing funding assistance to the growers to implement new tools has been incredibly important to achieving the goal.
Innovation requires investment and the mayor said by backing research and offering funding assistance, local government, with the support of the county and state, is ensuring regional growers have the tools they need to lead the way into the future.
Fetick commended Michael Wolfin, the assistant research professor of entomology at Penn State University where he runs the Mushroom Fly Research Team. The mayor said this research his team has achieved at Penn State has built a solid framework to long-term solutions. He said both the Pennsylvania Department Agriculture and Penn State have held an ongoing commitment to finding Aaresilient roadmap for lasting impact.
Members of Penn State’s Mushroom Fly Research Team share a moment in the sunshine in July 2024. The team is dedicated to finding solutions to eliminate the phorid fly in support of Chester County’s residents and mushroom farmers. (Courtesy of the Mushroom Fly Research Team / Penn State University)
“Having access to affordable tools to mitigate the phorid fly benefits the growers and the nongrower community that is so negatively impacted,” Fetick said in regards to the phorid fly.
“We are making progress,” the mayor said.
For ” leading the charge in Harrisburg to keep this issue on the front burner” the mayor thanked state lawmakers including Rep. Christina Sappey, D-158th of East Marlborough, John Lawrence, R-13th of West Grove, Sen. Carolyn Comitta, D-19th, of West Chester, Sen. John Kane, D-9, of Birmingham.
Kennett Square Borough Council President Bob Norris said the community is grateful for Governor Shapiro’s support and dedication to enhancing the well-being of local residents and strengthening the mushroom industry across the region.
The rapid proliferation of the phorid fly has reached a critical level, necessitating urgent state intervention and mitigation efforts. “They are annoying to everyone and cause a huge economic impact to the mushroom growers,” Norris said.
“The mushroom industry is a key part of our local economy,” Norris said. “Anything that can help them maintain the vital role they play is beneficial. They employ many people and support many local initiatives and nonprofits. Having the state work with the industry and local governed to improve the situation is much appreciated.”
“I am very grateful for the expanded quarantine order and Best Management Practices,” Sappey said. “The increased resources the department is deploying to combat the phorid fly issue in our county demonstrate the high level of commitment necessary to support not only our residents, but our mushroom growers challenged by lower yields who are in need of resources to employ best practices. I’m also pleased with the accountability measures included.”
“Any effort by the Commonwealth to reduce and eliminate the phorid fly infestation is to be encouraged and applauded,” said Kennett Township Supervisor Geoff Gamble. He commended Sappey for her work in this respect.
“However,” Gamble said, “in the end it is results and not efforts that count.”
Phorid flies swarm on a crop of mushrooms in Chester County. (COURTESY OF THE MUSHROOM FLY RESEARCH TEAM / PENN STATE UNIVERSITY)
In 2025 four municipalities — Kennett, Avondale, New Garden and Kennett Square — declared emergency resolutions to combat the phorid fly crisis impacting this region. The collective measures cited local public health concerns and the economy at the crux of this crisis in wake of the phorid fly increasing in population exponentially since 2012.
This past winter, the municipalities enacted new resolutions calling for more action to be done. The municipalities are Kennett Square, Kennett Township, New Garden Township, East Marlborough Township, Avondale Borough and Penn Township.
“I truly appreciate the opportunity to collaborate with our Southern Chester County neighbors on working towards a solution for our residents and growers,” said Fetick. “We have been unified in our efforts to solve this problem as a collective.”
Inside the windowless farms, growing mushrooms happens in dark, damp settings 24/7. Many people in mushroom houses are undocumented workers who represent the bulk of the agriculture workforce for this industry in the Commonwealth.
Pennsylvania produced 69% of mushrooms sold in the U.S. in the 2024-25 growing season, according to Penn State University.
Kennett Township Supervisors’ Chairperson Pat Muller said she is extremely pleased that the Commonwealth has elevated the phorid fly problem beyond a regional concern.
“I feel that with the integration of real science and political will that visible improvement will be seen soon,” Muller said.
“I am grateful and encouraged with this announcement from the Commonwealth,” said Kennett Township Supervisor Mike Bailey. “There’s no silver bullet to this problem.”
Bailey said with this initiative, Kennett hopes to see a real reduction of phorid flies, noting that will take time to achieve.
Kennett Township Manager Alison Dobbins said there are 15 mushroom growing businesses in the municipality.
A given business can own and operate dozens of windowless, climate-controlled cinder-block buildings designed to be kept dark for fungi growth and cultivation. Locally these structures are referred to as mushroom farms.
“By giving mushroom farmers tools to control pests and financial support to help them do it,” Redding said, “the Shapiro Administration is showing that we are committed to helping farmers protect their valuable crops so they can continue to produce top quality products to feed Pennsylvania’s economy.”
The revised order, effective March 23, requires all mushroom growers in Chester County to steam-treat mushroom houses between crops, as well as the medium used to grow prior crops. Steam treatment, or pasteurization, kills adult flies, larvae, bacteria, fungus, and pathogens, preventing spread to adjacent farms or subsequent mushroom crops, according to the Pennsylvania Department of Agriculture. “The method is an industry-proven, effective practice for managing the spread of the pest.”
Further, growers must keep records of treatments and the number of insects present. They must also implement one of five additional treatments proven effective in controlling the pests:
Exclusion and Inclusion Method, sealing entry points and eliminating attractants:
Parasitic Nematodes
Predatory Mites
Adulticides, insecticides that kill adult flies
Long Lasting Insecticide Nets
“Penn State brings some of the top specialists — not just in the nation, but in the world — to the conversation,” Lawrence said. “As it relates to specialty agriculture in general and mushrooms in particular, they are putting significant resources and research into this.”
The lawmaker said the Pennsylvania Department of Agriculture and Penn State are “leading together.” He said they have united with “an all-hands-on-deck response to a major quality of life issue and a very difficult issue to resolve.”
“I applaud Governor Shapiro for stepping in to address the Phorid fly issue we are facing in Southern Chester County,” said Kennett Square Borough Councilman Juan Luis Tafolla. “I believe this is a step in the right direction, and I look forward to seeing what my fellow elected officials and community leaders do next.”
“While West Grove Borough is not impacted nearly at the levels of some of our neighboring communities, we understand the challenges phorid flies represent to residents in those communities,” said Borough Manager Greg McCummings in West Grove.
“The mushroom industry is a critical part of the economy for Southern Chester County, and its impact is felt across the entire region, including West Grove,” he said. “While it’s difficult to quantify how many of our residents work in the industry, we know the numbers are significant.
McCummings said West Grove applauded the investment the Pennsylvania Department of Agriculture is making, noting this action is an important step to combating the phorid fly issue while also supporting the industry as a whole.
“An industry who’s impact is monumental to our region,” McCummings said, “and reaches well beyond Southern Chester County.”
“American Mushroom members have a long history of crafting and leading best practices in their growing processes and environmental best practices, and member farms currently apply the practices cited in the Governor’s updated quarantine order,” said Rachel Roberts, president of American Mushroom Institute, a trade association for American commercial mushroom businesses and suppliers based in London Grove.
“Current research on the phorid fly challenge is dynamic, and since 2014, the mushroom farming community in Chester County has worked with and will continue to work in tandem with researchers to understand this shared pest and find realistic solutions,” she said.
Chester County Commissioner Marian Moskowitz lauded the additional support and a clear, countywide approach to addressing the phorid fly issue provided by the Pennsylvania Department of Agriculture and Penn State.
“Chester County’s mushroom industry is a cornerstone of our economy, and this funding gives growers important tools to manage a very real challenge,” Moskowitz stated. “This should also give relief to our residents who are dealing with these flies in their homes and neighborhoods — this has been incredibly disruptive. This effort reflects the balance we need: supporting our farmers while also protecting the quality of life for the communities around them.”
While serving as a state representative, Eric Roe held a town hall in Kennett Square on Feb. 12, 2018. He said the meeting was conducted entirely in Spanish with immigrant workers from the mushroom industry. “We discussed the phorid fly problem, among other issues,” Roe said. Today, Roe is a Chester County commissioner. (DLN File Photo)
“While I am always eager for new ways to combat the phorid fly issue, I wish the Governor’s administration were better about working with the mushroom growers,” said Chester County Commissioner Eric Roe.
“Many growers have come to me and said they’ve been kept in the dark about the state’s ever-changing regulations. Meanwhile, the mushroom growers want the flies gone just as much as the nearby residents,” Roe said.
“This problem cannot be fixed without the input of the farmers themselves. If Harrisburg bureaucrats don’t properly inform or solicit feedback from our local mushroom growers, they might inadvertently harm an important industry yet still fail to rid us of the flies,” Roe said.
“Mushrooms thrive when they’re left in the dark,” Roe said. “People don’t.”
Fungi festival
In other news, the 41st annual Mushroom Festival returns September 11 through September 13.
This popular event draws tens of thousands of people from across Southeastern Pennsylvania, and the nation, to Kennett Square.
This shroomin’ good time features a lively 1-mile street fair with a happy, family-friendly environment that is full of fungi celebrations, laughter and culinary delights in the Mushroom Capital of the World.
Kennett Square is home to an annual weekend Mushroom Festival in the heart of the borough each September. (COURTESY OF JEN SAMUEL)