ST. LOUIS — Now that the emerald ash borer has made its way to Missouri, state experts doubt they can stop its spread. Their focus is on slowing it down.
Seven emerald ash borers were found in July in traps at Greenville Recreation Area in southeast Missouri's Wayne County. The small, metallic green beetle is native to Asia. Its larvae burrow into the bark of ash trees, causing trees to starve and die.
The beetle was first found in Michigan in 2002 and has reached at least seven other states, killing tens of millions of trees along the way. Missouri is the farthest south and west area with a known infestation.
"Other states have spent millions of dollars fighting this," Hank Stelzer, University of Missouri Extension forester and a member of the state's Emerald Ash Borer task force, said Tuesday. "We're not going to eradicate it. Slowing the spread is what we're trying to do now."
Doug LeDoux, pest survey coordinator for the Missouri Department of Agriculture, agreed that eradication is unlikely, in part because property owners may not recognize the symptoms for years after a tree is under attack.
"The beetles hit the tree from the top down and it's very difficult to see the damage the first couple of years," he said.
Ash trees make up about 3 percent of Missouri's forests and as much as 14 percent of trees in cities and towns. The trees are popular in urban settings — thousands in Forest Park in St. Louis are ash. Stelzer estimates that 85 percent of the trees on the grounds of the Gateway Arch are ash.
Communities and homeowners like ash trees because they don't create much of a mess and provide nice shade.
If and when ash borer infestations hit urban and suburban areas, "it's going to be traumatic," Stelzer said. "We're encouraging municipalities to get a survey in place and start to know what they're going to do when it shows up."
When that will be is anybody's guess. To slow the movement, state and federal officials are cutting down ash trees within a two-mile radius of the site where the first ash borers were found. And last month, the state ordered a quarantine of ash wood, ash products and hardwood firewood from Wayne County. Any ash or firewood coming out of the county must be heat-treated to kill the insects.
While only discovered in July, officials now think the ash borer has been at the Greenville site for much longer. Survey work conducted by state and federal experts indicates the pest has been there at least five years, maybe longer.
Officials think the ash borer found its way to the recreation area through firewood brought in by campers. Stelzer encourages anyone who uses firewood for camping or home use to "buy it locally and use it locally."
The good news is that, so far, the ash borer has not been found elsewhere in Missouri. Still, Stelzer said homeowners with ash trees should be vigilant.
Signs of infestation include increased woodpecker activity — they feed on the larvae — and a yellow, thinning crown. The insects leave a D-shaped mark when they exit the bark. But because they tend to start at the top, once the exit holes get low enough to be seen, it's probably too late to save the tree.
A new chemical is being tested and shows promise, but it's expensive, Stelzer said. LeDoux said parasites that could kill the beetles are also being bred, but it isn't clear when they'll be available.
The experts encouraged anyone planting new trees to avoid a large number of ash.
"No one species should occupy more than 10 percent of plantings," Stelzer said. "It's just like the stock market — you want to diversify."