Pennsylvania mushroom farmers mount new defense against fungal foe

A tiny pest is causing big problems for Chester County, Pennsylvania's $1.3 billion mushroom industry. Now, one farm is fighting back with a new way to keep the flies away.

Sher-Rockee Mushroom Farms in Upper Oxford Township is a family-owned business and on-site farm market that produces about 200,000 pounds of mushrooms every week. Many of those mushrooms end up on grocery store shelves around the region. But two years ago, the farm lost about half of its crop to the phorid, or scuttle fly.

"We're a mid-sized farm, so every penny counts for us," Alec Vazquez Ciarrocchi said. "So losing that production was a huge blow to our farm."

The scuttle fly destroys 10% to 40% of mushroom crops annually, according to the Pennsylvania Department of Agriculture. The pest has also become a nuisance for residents in communities near mushroom farms.

Each phorid fly can lay many eggs. Their larvae feed on mycelium, the thread-like network that mushrooms grow from.

After years of searching for a solution, Sher-Rockee found a technique that uses pesticide-infused nets to target the flies. When a fly comes into contact with the treated net, it dies within 10 to 30 minutes.

Vazquez Ciarrocchi said the farm partnered with Swiss company Vestergaard, which developed insecticide-treated mosquito nets designed to kill mosquitoes on contact and help prevent the spread of malaria in certain parts of Africa. The company also developed pesticide-treated nets for commercial mushroom farmers.

"Since we put the nets in, we haven't really seen much loss," Vazquez Ciarrocchi said. "Now flies haven't even really been an issue on our farm."

The nets are only used during the spawning phase and are removed about 12 days later so the mushrooms can continue to grow.

Vazquez Ciarrocchi credits Penn State entomology professor Michael Wolfin and his students with helping the farm discover a solution. Wolfin and his team spent years researching the fly and testing different ways to control it at the farm.

"Right now my job is to make the lives of people in Pennsylvania better and I'm really lucky that I got to do that," Wolfin said. "Sher-Rockee Mushroom Farms is an exciting sort of test case of what can happen when researchers, scientists, entomologists and farmers come together and work together to solve a problem."

Vazquez Ciarrocchi said he is grateful to Wolfin for his work.

"He's a great person," Vazquez Ciarrocchi said. "I consider him a friend now. He reaches out to me all the time."

The farm is also working to keep the flies from getting inside in the first place. Pesticide-infused nets are placed over air ducts on the roof, and bird feeders around the property attract the scuttle fly's natural predators, including purple martins.

The American Mushroom Institute, a trade organization representing mushroom farmers, said it helped secure $250,000 from the Pennsylvania Department of Agriculture for phorid fly mitigation, including fly netting and compliance tools for growers.

The institute also said it helped secure EPA approval of a new phorid mitigation tool for mushroom farms, as well as hundreds of thousands of dollars from the U.S. Department of Agriculture for a fly-counting system.

"We are working very hard to put resources into the hands of the growers to deal with this crop-harming pest and to assure we remain good neighbors in the community," Rachel Roberts, president of the American Mushroom Institute, said.