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Chester County Press

Scientists announce progress against Phorid fly scourge

02/08/2021 11:38PM ● By Steven Hoffman

A team of scientists from Pennsylvania State University that is working with local mushroom growers is making progress in the battle with the Phorid fly scourge.

Phorids have been terrorizing homeowners and devastating mushroom crops in the southern Chester County area since the major control pesticide, diazinon, was banned for use on the fungus by the Environmental Protection Agency in 2012.

On Jan 28, State Rep Christina Sappey, who represents the 158th district, held a virtual meeting to share information about recent work on the problem. During that meeting, the scientists reported results of a fairly successful advancement which on one farm has come close to eliminating the flies entirely.

Presenting during the virtual meeting were Penn State Mushroom Pest Research Team members Mike Wolfin, Tom Baker and Nina Jenkins; local legislators state Sen. Carolyn Comitta (D-19) of West Chester, state Rep. Craig Williams (R-160) of Glen Mills, and state Rep. John Lawrence (R-13) of West Grove. Pennsylvania Secretary of Agriculture Russ Redding also presented an overview of the problem at the state level.

The positive innovation was the topic of much of the meeting and it involves an electrostatic window screen infused with an approved insecticide that kills the flies as they go through the grid both coming in and going out during their life spans.

Wolfin, an insect behaviorist ecologist, spoke at length about how he researched and developed the screen, as well as how it works. Much of the information he gained since he began the project in 2017.

He said he at first had to learn about the behavior of the flies – where they are born, what they eat, how they breed and where they travel.  He referenced the behavior of the flies, noting that their numbers increased dramatically in 2012  when the Environmental Protection Agency no longer allowed the renewal of the diazinon label for mushrooms.

Early on, he determined that these insects, which devastate crops and annoy homeowners, are born and feed exclusively on mycelium in the mushroom houses. Mycelia are the fine, white filaments that form networks on the mushroom-growing beds and are analogous to the roots of the mushrooms themselves.

It is there that they spend several weeks progressing from eggs to larvae, growing and feeding and harming the coming crop. When they become adult flies, they exit the mushroom-growing rooms, seeking light and to mate.

It is during this departure from their birthplace into the outside that their swarms are often blown to neighborhoods and, because they like moisture and high places, often find their way into people’s bathrooms and other areas of the homes.

At this point, Wolfin said he often hears fears from homeowners about the dangers of phorid flies. He said he wants people to know that at least three myths have been proven to be false: Phorids don’t eat or grow anyplace except mycelium, they don’t sting, and they don’t spread disease. They are, however, a terrible concern for homeowners when they invade a house or neighborhood.

It was with the comings and goings of the phorids to and from the mushroom houses that led Wolfin to develop his fly-killing screen.

He constructed lighted electrostatic screens on which he applied the allowed insecticide EcoVia.

In the case of the Sher-Rockee Farm in Upper Oxford, where he conducted much of his research, each mushroom house has one upper level vent into which he placed the screens. Simultaneously, he trained some of the harvesting staff to monitor the screens and apply the EcoVia on a regular basis.

At the first try, the phorids did not seem to be reduced after intervals of several days of application. However, when the insecticide was applied every day, there was a substantial diminution to the point where the farm became almost free of the flies.

Hector Martinez, who is in charge of monitoring the screens at Sher-Rockee Farm, said, “They don’t come back.”

Wolfin said the success of the program has prompted several other mushroom farms, notably Phillips and Brownstone, to begin trying it soon.

One “negative” about the screens, he said, is that each mushroom farm is different: the architecture, the protocols, the layouts. So, whereas Sher-Rockee has one vent per house at the upper level, other farms may have houses with several vents per house at different levels. In effect, there is no unified method for installation.

Secretary Redding, in his overview of the topic, said that while the elimination of the flies in the mushroom houses is important, there is also the responsibility of the Department of Agriculture to address the homeowners who are invaded by the flies.

This sentiment was seconded by Williams, who said some of his constituents are desperate to rid their homes of phorids. “They tell me ‘They’re in my baby’s eyes and in our food,’” he said.

Williams added to all who were tuned into the presentation that he is eager to hear from people with the problem so he can advocate for them at the state level for financial support to keep fighting the scourge.

Lawrence said he can attest to the problem of phorids in southern Chester County because he was personally affected by them in his office.

When Wolfin was asked about research into the problems with flies in residential dwellings, he said there has not been home or neighborhood research. However, he added, if the flies are eliminated from the mushroom houses, where they hatch, eat and then die in the screen on the way out to mate, then the numbers will likewise go down in homes.

At the conclusion of the meeting, Comitta praised the research team and said, “We will work together to find the dollars to get over the finish line on this.”

Redding said he appreciated the work and mission of Penn State as a land grant institution and its research team. “You have our commitment to continue and work to find what is the next step on this to help the team,” he said.