By Richard L. Gaw
Staff Writer

In a groundbreaking announcement, Pennsylvania Agriculture Secretary Russell Redding announced that the state’s Department of Agriculture has issued a mandatory quarantine order to all mushroom growers in Kennett and New Garden townships to help control the recent infestation of the phorid fly, a destructive pest causing that is causing crop damage to mushroom farms in Southeast Pennsylvania and creating a nuisance for nearby homeowners. 

The quarantine order went into effect on Jan. 30 and requires growers to steam-treat between crops as prescribed in step-by-step instructions accompanying the order. Growers are required to keep records of treatments and submit reports to the department, and growing facilities will be subject to periodic inspections.

The order requires all mushroom growers to steam-treat or pasteurize mushroom houses and previously used growing medium between crops. The treatment method – which is an industry-proven and effective practice for managing the pest -- kills adult flies, larvae, bacteria, fungus, and pathogens that prevents the spread of the flies to adjacent farms or subsequent mushroom crops. 

“We have been working closely with the mushroom industry and Penn State researchers for many years, seeking safe and effective solutions to this persistent pest plaguing one of Pennsylvania’s most valuable crops,” Redding said. “Steam treatment has proven to be safe and effective, but the method only works if 100 percent of growers use it.”

With 465.8 million pounds worth nearly $531 million produced in 2023, Pennsylvania leads the nation in agaricus mushroom sales and production. The center of the state’s mushroom industry is Chester County, where approximately 2,000 mushroom houses are located.

While the proliferation of phorid flies is nothing new to the mushroom industry, the volume of infestations have risen dramatically and consistently over the past decade and wreaked havoc on the product, due in part to warming temperatures and increased year-round humidity. The pest has been shown to reduce mushroom crop yields by up to 40 percent.

The flies invade the growing rooms through every possible opening and crack and lay eggs in the substrate, casing layer, and on the mushrooms themselves. Subsequently, the larvae that appears from the eggs five to 10 days after hatching is known to damage to the mushrooms.
In addition to the yield losses that larvae cause, the mushrooms lose their marketable appearance because of the larvae that swarm on their surface. Larvae also enter fruit bodies, forming many passageways and holes, which makes the mushrooms unsuitable for use.

The mushroom industry currently has multiple insecticides, fungicides, and herbicides labeled and approved for use controlling phorid flies and steam treatment is a critical element of the control methods accepted by the industry as a best management practice.

American Mushroom Institute (AMI) President Rachel Roberts said that many in the industry need support and resources to meet their commitments to being good neighbors. 

“AMI members continue to test and develop strategies to combat phorids and they stand ready to adopt new tools and practices based on the research conducted with the industry,” she said. “We welcome this significant investment from the Department of Agriculture to assist farmers and the community.”

The Pennsylvania Department of Agriculture has funded nearly $445,000 in research to develop safe, effective control methods for phorid flies. The department continues to work with the U.S. Department of Agriculture and Penn State University, as well as other industry experts, to support research to develop safe, effective pest control methods that do not use chemicals that may harm the environment and jeopardize food safety and human and animal health.

‘A fair and effective way’ to address the problem

“I am extremely pleased that the Governor and the Department of Agriculture have heard our urgent requests for assistance and are taking action to help residents in the 158th impacted by phorid flies,” said State Rep. Christina Sappey, who has held several in person and online public meetings with residents, elected officials and experts in the field of mushroom growing operations about the Phorid Fly. “While Penn State has been making steady progress on mitigation research, we need to do more, and the direction coming down today will ensure this proven method is being adhered to and that smaller mushroom operations needing assistance to comply have access to grant funding.  

Sappey continues to advocate for more state funding to explore finding ways to eradicate the phorid fly.

“My direct outreach to the Ag Department requested an update to Pa. Agriculture Best Practice Management to include indoor agriculture, specifying methods for the mushroom industry to employ to mitigate negative impacts such as phorid flies,” she said. “It is important to note that this quarantine order does not quarantine mushrooms or mushroom farms. It is the vehicle, prescribed under the Pa. Plant Pest Act, for this treatment order. 

Sappey called the mandatory order “a fair and effective way” to treat a problem that has continues to be a persistent nuisance for area residents.

“There are clear guidelines, help for small operators and accountability that will be enforced by the Chester County Conservation District,” she said. “I’m grateful to the Shapiro administration, our local municipalities and the American Mushroom Institute for their collaboration, and most importantly, our residents for their engagement and patience.” 

Sappey said she has also requested the Department of Agriculture to update the state agricultural best practice management to include indoor agriculture.

‘The beginning of a long-term solution’

Last December, Kennett Square Mayor Matt Fetick called the phorid fly infestation “a true emergency in our community and the greater region,” and promptly signed an emergency declaration on Dec. 2 that called for “a comprehensive, multi-agency approach to eliminate the phorid fly infestation” by enacting six initiatives that among them included the need for the Commonwealth to pursue additional state funding to research mitigation controls through Penn State; incorporate education tools for mushroom growers about mitigation controls; and enact state regulations to allow growers to implement safe pest controls.

“I’m thrilled that our Emergency Declaration received attention and action in Harrisburg,” Fetick wrote in an e-mail to the Chester County Press. “This marks the first time that the Department of Agriculture has taken official action to require the implementation of best practice management and further put into place a mechanism for tracking compliance. The phorid fly issue impacts growers and non-grower residents. Having mitigation procedures in place is a great first step.  

“I look at this step as the first of what may be several steps needed to combat the problem fully. I have been in direct communication with Secretary Redding and the Governor’s office on this issue. I will continue to advocate on behalf of our residents to make sure that we do everything we can to solve this problem. 

“This is not a one and done. This is the beginning of a long-term solution that will benefit growers and residents alike.” 

In conjunction with experts from The American Mushroom Institute and Penn State Extension, the department will hold educational sessions for growers in English and Spanish.

Mushroom farmers seeking financial assistance with implementing the requirements may contact the Chester County Conservation District at 610-455-1381 to apply for grant funding.

To contact Staff Writer Richard L. Gaw, email [email protected].