UNIVERSITY PARK, Pa. — When they first showed up in 2012, Anne Kelly had no idea what the insects were.
“I had a day off from work and decided to clean my deck doors, and I saw all these little bugs,” Kelly, a resident of a development in southern Chester County, recalls. “They look like tiny gnats. I cleaned them up and went about my business. But they were back within an hour, and then they were all over my ceilings and windows. That was just the beginning.”
Kelly hired several exterminators, but they could not figure out where the insects were coming from. At her wits’ end, she took her dog and cat out of the house and had a bug bomb set off. But the mysterious “gnats” were back the next day — even more than before.
Kelly and her neighbors did not realize the swarms of tiny insects were mushroom phorid flies that came from a nearby mushroom farm. And she didn’t know that the U.S. Environmental Protection Agency had just ruled that diazinon — an insecticide that mushroom growers had used for decades to control the pest — could no longer be used in mushroom production because of its toxicity. That decision left mushroom farmers without a control product.