There's a fungus among us, and it's keeping Eastern hardwood forests healthy and helping to save Pennsylvania more than $1 million this year.
More than 130 years after gypsy moths first took hold in American forests, a fungus that kills the moth larvae is helping to keep moth populations in check in several states.
As a result, the Pennsylvania Department of Conservation and Natural Resources said it does not need to spray for gypsy moths this year. Delaware also won't spray this year, and damage caused by the moths was down in neighboring states.
"There just isn't enough of a gypsy moth population out there to justify a spray program," said Kevin Carlin, an entomologist with the Pennsylvania Bureau of Forestry.
Much of the credit belongs to Entomophaga maimaiga, an Asian fungus that sickens and kills the moth larvae. The fungus has spread throughout most of Pennsylvania and Virginia and across wide swaths of several other states, helped by cool, wet spring weather in 2001 and 2002.
Gypsy moths defoliated about 238,000 acres of Pennsylvania hardwood forest in 2001, but that number dropped to 56,000 acres last year. The state spent nearly $1.5 million to spray more than 58,000 acres last year.
"Over the past several years, [Entomophaga] has established itself across the Commonwealth," Carlin said. "As a result, it's having a major impact on gypsy moth survival."
Officials in Maryland and West Virginia reported similar findings.
If moth populations remain low, other states may also see fiscal benefits.
"All the states this year, from Virginia to Wisconsin, are looking at heavy budget cuts and reduced staffing," said Amy Onken, an entomologist with the U.S. Forest Service in Morgantown, W.Va. "This is a good year for the gypsy moth to be down."
That's not a first, but it is a noteworthy accomplishment.
Gypsy moths arrived in the United States in the 1860s, brought by a college professor who sought to breed a hardy variety of silkworm. The first infestation was reported in 1869 in Medford, Mass., and the moths have since spread throughout the Northeast and mid-Atlantic states.
The infestation continues to move west along a line that begins on the North Carolina coast and crosses Virginia, West Virginia, Ohio, Indiana, Illinois and Wisconsin to Michigan's Upper Peninsula. Isolated outbreaks have been recorded in several other states.
The moth reached Pennsylvania in 1932, and the state's first spraying programs were in place by the end of the decade. Still, the moths thrived among Pennsylvania's abundant hardwood forests, feeding on stands of mature oak before spreading to maples and hemlocks.
"There were periods where, driving through western Pennsylvania on the Turnpike, you would have to use your windshield wipers with washer because so many of the flying moths were hitting the windshield. There were places they had to put sand at intersections because the number of larvae that were being run over by cars was creating a slippery situation," Carlin said. "It was just an uncontrolled, invasive insect."
Spraying has continued with rare interruptions since the late 1930s, and in the early 1980s state foresters introduced both parasites and insect predators that have helped contain gypsy moth populations.
But it wasn't until the accidental introduction of Entomophaga in the late 1980s that gypsy moth populations began to fall dramatically.
That doesn't mean Pennsylvania has seen the end of the gypsy moth. A warm, dry spring would hurt the fungus, and gypsy moth populations are subject to natural cycles, meaning populations can be expected to rebound in the future.
But the combination of Entomophaga and government control efforts mean it's unlikely that gypsy moths in Pennsylvania will reach the numbers they once did.
"We don't ever expect to see the large million-acre-plus outbreaks that we saw in the past," Carlin said.