Endangered trees: Making a hash of the ash THE scourge has come in from Asia and has destroyed tens of millions of ash trees in America. Now Massachusetts has become the latest state to impose a quarantine on ash-wood in an effort to halt its spread. The emerald ash borer has already wrought havoc in 17 other states and in Canada, depleting stocks of a valuable hardwood used to make baseball bats, flooring, tool handles and kitchen cabinets, among other things. The metallic green beetle was discovered in Michigan in 2002, but US Forest Service researchers say it probably arrived years earlier in wooden packing material aboard a ship that docked near Detroit. The flying beetle can kill a healthy, decades-old ash tree in a mere three to five years. It lays its eggs on their bark, which the larvae, once hatched, bore into and consume, eventually starving the tree of water and nutrients. Adult borers can fly only relatively short distances between trees, but people spread them widely when transporting firewood. Hence quarantines such as the one imposed in Massachusetts on March 1st. All the other states that have found the beetle have introduced similar measures. The restrictions on untreated ash (the wood can be made safe by heating it in a kiln) in Berkshire County, Massachusetts, came after the insect was found there late last summer. At local hearings wood harvesters protested about the impact the rules will have on their industry, which earns roughly $485m a year, and of which up to 20% consists of ash. One consolation for them is that neighbouring New York recently added 22 counties to its own quarantine area. Now that Berkshire is also safely quarantined, that means harvesters will be able to again move ash to mills situated just across the border. Environmental workers, meanwhile, have set beetle traps across the state and "girdled" dozens of trees, removing strips of bark to attract and then capture the borers. But their efforts have proved ineffective, and Massachusetts, like other affected states, now hopes merely to delay the insect's advance. Researchers are studying new ways of fighting it, including the introduction of natural predators, such as a certain type of wasp from China. Without a breakthrough, however, biologists fear the hungry insect will wipe out all the ash trees in North America.