St. Louis suburbs preparing for ash borer invasion

CHESTERFIELD, Mo. -- The emerald ash borer has already forced the removal of hundreds of trees on the grounds of the Gateway Arch in St. Louis. The invasive insect is now causing worries in the suburbs.

Suburban St. Louis towns are working to preserve their green space, the St. Louis Post-Dispatch reported. Chesterfield, Richmond Heights, Ballwin and St. Peters are among the places with large numbers of ash trees, making them susceptible to a potential economic problem if the insects invade, and eventually kill, trees.

A gradual schedule of culling the ash trees has prevented some cities from the financial hit.

"When the emerald ash borer does get here, we want to have a manageable problem rather than a disaster," said Mindy Mohrman, an urban forester for Chesterfield, Missouri.

The emerald ash borer is native to China and eastern Asia. The half-inch-long, emerald green beetle was first detected in the U.S. in 2002 and has been identified in 23 states. The insect was first discovered in Missouri in July 2008 in Wayne County, and has since spread.

In October, the National Park Service began removing about 1,200 ash trees at the Gateway Arch. About 800 of those trees are expected to die because of the invasive beetle. As part of the project to renovate the Arch area, more than 4,100 new trees are expected to be planted in 2016.

So far, the beetle hasn't shown up in St. Louis County, but it was found in Lake St. Louis in St. Charles County.

Once infected, a tree usually dies within two years, Mohrman said. Removing and replacing an ash tree costs, on average, about $1,000 per tree, Mohrman said.

Chesterfield is responsible for maintaining about 7,000 ash trees, and the city's budget allows for the removal of about 700 trees a year. Mohrman has been able to include ashes that are already dead or in decline from other diseases or just age. No healthy trees have been taken yet.

Ballwin's urban forester, Will Rein, is working on a plan to remove about 2,300 ash trees, nearly 30 percent of the tree population the city maintains.

"We're still trying to figure out how it's going to impact our budget," he said.

Richmond Heights' urban forester Tim Brunsman said that because the beetle attacks the tree's circulation system, limbs can fall off, presenting a threat to public safety and property. Richmond Heights has gotten its ash population down to about 100 trees since 2008 and is able to remove and replace the trees within its regular budget, he said.

"You don't want hazards out there for whatever reason," Brunsman said.