The Pennsylvania government has expanded its quarantine guidelines to help Chester County farms combat the phorid fly crisis, writes Jen Samuel for The Daily Local News.
The invasive pest destroys roughly 40 percent of the region’s mushroom farms each year. The flies also appear inside homes and residential areas, causing further distress for residents.
As the mushroom capital of the world, Kennett Square produces 60 percent of all mushrooms grown in North America. Phorid flies thrive off of plant material grown in the county’s windowless mushroom farms with dark, damp growing environments.
In 2025, four Kennett-area municipalities declared emergency resolutions regarding the phorid fly crisis. Much of the regional economy relies on mushroom farming and agriculture, and fly populations have increased since 2012.
However, thanks to new governmental guidelines, precautions are in place.
A revised government order, effective March 23, requires Chester County mushroom growers to steam-treat mushroom houses between crops. Steam treatment, similar to pasteurization, kills larvae, bacteria, and other pathogens to prevent the spread of the pest to additional crops or nearby farms.
Farmers will also implement one of five additional guidelines, including sealing entry points and using insecticide nets.
While it will take time to see the real reduction in phorid flies, farmers and township officials are optimistic about the outcome.
About the teamwork it’s taken to manage the crisis, Kennett mayor Matt Fetick said, “I truly appreciate the opportunity to collaborate with our southern Chester County neighbors to work towards a solution for our residents and growers. We have been unified in our efforts to solve this problem as a collective.”
Read more about ongoing PA governmental protections against the phorid fly crisis in The Daily Local News.
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Editor’s Note: This post first appeared on VISTA Today in March 2026.
