ANDERSON, Ind. — A tiny green beetle that decimates ash trees is nibbling away at traditional summer campfires as states try to halt the insect's spread through infested firewood that campers unwittingly haul into parks.

Indiana, Ohio and Michigan -- where the emerald ash borer has been located -- have imposed tough rules on bringing wood into parks and moving live ash trees or logs out of infested areas.

Wisconsin and South Dakota have banned out-of-state firewood outright, and other states are keeping a wary eye on the bug, which has killed nearly 20 million North American ash trees in the three infested states and southern Ontario.

The iridescent green beetle was found in Michigan in 2002. Experts say it likely hitched a ride years earlier from Asia in wooden packing crates. Campers, hunters and city dwellers heading off to cottages for weekend excursions have spread them rapidly by bringing their own firewood along for outings, experts say.

"It's almost done unconsciously when you go camping -- you pack your cooler and your tent and your firewood and you head out," said Sharon Lucik, a spokeswoman with the U.S. Animal Plant and Health Inspection Service in Brighton, Mich.

Because the ash borer's native range is in Asia, it has no natural predators in North America. Trees can be treated annually with chemicals to combat the larvae, but that isn't an economical option for vast forest expanses, tree-lined streets and suburban yards, Lucik said.

She said the federal agency's goal is for states to keep ash borer populations confined to infested areas so the beetle will be easier to combat if an effective form of control is found.

The beetle doesn't just threaten ash trees, a wide-ranging species valued for fast growth, shade and fall foliage in the wilderness. Ash wood, strong and light in color, is used in furniture and baseball bats, generating about $200 million annually, according to the American Forest & Paper Association.

In Indiana, the half-inch-long beetle has spread to seven counties since it was found in a campground in April 2004. This spring, the state banned campers from bringing firewood from those counties, as well as quarantined counties in Ohio and Michigan, into the state's 24 parks, nine reservoirs and various recreation areas.

Under the policy, park officials seize and burn wood if it's from one of the counties. Campers can buy borer-free wood at a park's supply store for $4 to $5.

Joe McGuinness and his father-in-law, Dan Greene, of Franklin, Ind., got a taste of the new rule recently at the 290-acre Mounds State Park, in central Indiana.

The gate attendant quizzed them about the firewood they'd hauled with them. McGuinness reassured her it came from a tree a storm knocked down in his parents' yard just south of Indianapolis, not from a quarantined county.

McGuinness said later he wouldn't mind if campers were banned from bringing any firewood into parks to halt the beetle's spread.

"Of course, it would cost a little bit if you had to buy it at the camp store, but it would be worth it to protect the trees," he said. "This is such a pretty place."

The ash borer's spread has been aided by the fact that infested trees are hard to spot, said Jodie Ellis, an exotic insects education coordinator at Purdue University. Adult beetles lay their eggs in a bark crevice, and hatched larvae bore tiny holes to get inside.

They grow into fat grubs that munch S-shaped tunnels through the layer of wood tissue that transports a tree's food and water, killing infested trees in a few years.

Illinois, which has nearly eradicated an Asian long-horned ash borer infestation after years of work, is closely monitoring the emerald ash borer's advance in Indiana, said Warren Goetsch, bureau chief of environmental programs for the Illinois Department of Agriculture.

Two years ago, Illinois launched a campaign to encourage park visitors to buy their firewood locally to avoid spreading a host of invasive insects, including the latest invader.

"The public's help is essential if we're going to detect this insect and stop it," he said.

Source: Associated Press