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.

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