Wilton’s ash trees under attack from invasive beetle

There may be a little less color in Wilton this fall. That’s because the emerald ash borer, a foliage-eating alien beetle, has been detected in Wilton.

Assistant Tree Warden Lars Cherichetti told The Bulletin he has seen trees killed by the beetle on Belden Hill Road.

“There are probably a number of other areas that have the beetle and I expect we will have a better idea of where this fall as we see more trees dying,” he said.

The emerald ash borer is an invasive species native to Asia, first noticed in the U.S. in 2002 in Michigan. It has since spread north into Canada, south to Tennessee, west to Minnesota and east to New York and now Connecticut. Cherichetti said the beetle was detected in Wilton last summer by monitoring wasps that feed on it.

Beetle eggs are laid in bark crevices. Much of the damage to the trees is done by the larvae, which feed on the trees’ conductive tissues, just under the bark, leaving what the Connecticut Agricultural Experiment Station describes as “tightly winding serpentine galleries” that can “very quickly stress and girdle an ash tree.”

They mature over the winter and the adults emerge — metallic green and about a half-inch long — to live about a month in the summer, feeding on ash foliage.

Cherichetti warned that trees here will start dying in large numbers as the beetle population grows.

“This is a concern for the Department of Public Works,” he said. “They currently have a backlog of town-owned trees that need to be taken down and are running low on funding. With no tree equipment or personnel trained in its use, the town subcontracts most of the tree removal work.  This will be a concern that will need to be addressed in the next few years.”

Based on a quick survey of roadside trees, Cherichetti estimates “we have on the order of 500 trees we will have to deal with.”

When asked about town-owned properties, he said the Town Forest in particular has a few ash trees, mostly in the southern part near Branch Brook. Other parts of the park are dominated by oaks, beech and maples.

“We will certainly notice the ash trees’ absence in areas where they are common,” he said.

Although there are no accurate surveys, Cherichetti thought 10% to be a good estimate of how much of the tree canopy is made up of ash trees.

“There are some areas where it is much higher,” he said. “In those neighborhoods it will feel like all the trees are dying.”

Cherichetti said people with ash trees on their property should consider whether to prevent infestation with insecticides or take trees down.

“It is possible to treat a tree for eight-to-10 years and still [cost] less than it would be to remove the tree, particularly if the tree is difficult to access with equipment,” Cherichetti said.

“Insecticide works as a preventative and is injected into the tree’s trunk so the chemicals are applied directly where needed.”

This is a restricted pesticide that must be applied by a certified arborist. It is a step neighboring Ridgefield is taking, which has also detected emerald ash borers. For the last four or five years, it has been treating some its high-profile ash trees, including those along Main Street.

The emerald ash borer is also wreaking havoc in Europe. Earlier this year the BBC reported the insect and the fungal disease ash-dieback could combine to wipe out ash trees in Great Britain.