The emerald ash borer has killed many ash trees since appearing in Kentucky in 2009, but arborists fear this could be the year when the voracious beetle really sinks its teeth into some of Lexington's most beautiful ash trees.
"I'm afraid it's going to be a lot worse this year," said Lexington-based consulting arborist Dave Leonard. "Already this spring I'm seeing a lot more ash trees not leafing out, which is not a good sign.
"It's been slowly building since we first saw the borers in the summer of '09. Now, it's crept inside New Circle Road, getting into bigger, older, more valuable trees."
Fortunately, even trees infested with ash borers can be saved if treated with chemical agents, said John Saylor, arborist-technician with the Urban County Division of Environmental Policy.
Smaller ash trees may be treated by home owners with over-the-counter products, Saylor said. But ashes larger than about 15 inches in diameter require professional treatment, he said.
Infected trees don't die overnight. But by the time owners notice their ash trees aren't looking well, it might be too late, according to Saylor. People who have ash trees and want to save them should consider treatment now, he said Monday.
The emerald ash borer is a bright-green beetle that has killed 50 million to 100 million ash trees since arriving in the United States from Asia in the 1990s. Its larvae bore through a tree's bark, feeding on sapwood and eventually killing the tree. The larvae are attractive dining for woodpeckers. Indeed, woodpecker activity on an ash tree is one sign the tree is infected.
Adult emerald ash borers emerge from infected trees in the spring by digging characteristic D-shaped exit holes, then fly away to infect more trees.
Lexington has large numbers of white, green and blue ash trees, and all are vulnerable to the emerald borer. The bugs seem to prefer white and green ashes, but they move eventually to the blue variety and kill them as well, experts say.
As recently as 2009, Kentucky had 131 million white ash trees, and 92 million green ash trees. A 2005 survey indicated that about 11 percent of Lexington's street trees were ashes. Exactly how many ash trees have been killed by the borers here isn't known.
But Saylor, who was driving around Lexington neighborhoods Monday to assess damage, said untreated ash trees essentially have been wiped out in some areas.
"We're three springs out from the borers first being detected in Lexington, and when you go back over and look at those areas you can tell pretty easily who treated and who didn't," he said.
Saylor said writing orders directing the removal of dead ash street trees has become a routine part of his job.
Leonard said ash trees in Lexington that have been treated are doing well. That includes some large old ash trees at Ashland, the Henry Clay Estate that were here when Clay came to Kentucky in the 1790s. Indeed, it was Lexington's ash trees that prompted Clay to name his estate Ashland, a name later adopted by towns in several states.
"Trees that are 10 to 15 percent infested by borers can be easily salvaged," Leonard said. Treatment becomes harder, however, as the borers tunnel deeper into the tree, he said.
More than one treatment might be needed, depending on the size of the tree and the kind of chemical used.
"There is a myth that big trees cannot be treated," Leonard said. "There are some treatments you can't do on big trees, but there are other treatments that do work. Any size ash, if it's in good condition, can be preserved."