Emerald ash borers are an exotic, green-metallic beetle native to Asia that measure about 8.5 millimeters long as adults. They are thought to have hitched a ride in cargo crates to Michigan in 2002.
Emerald ash borers are an exotic, green-metallic beetle native to Asia that measure about 8.5 millimeters long as adults. They are thought to have hitched a ride in cargo crates to Michigan in 2002.

April 20, 2018

An invasive beetle that kills ash trees has infested at least one tree in Carroll County, state entomologists recently confirmed.

It’s the first time evidence of the emerald ash borer has been found in the county. The beetle has spread to 32 states in the past 16 years and killed tens of millions of trees since it was first discovered in Detroit, according to a report issued by Dustin Vande Hoef, a spokesman for the state Department of Agriculture and Land Stewardship.

The beetle was found in far northeast Iowa in 2010 and last year in Greene County.

State officials have not revealed the exact location of the Carroll County infestation but said it was west of the city of Carroll. Entomologists — scientists who specialize in insects — found the telltale meandering scars in the tree’s bark as well as a dead beetle.

The beetle’s larvae feed on the trees’ inner bark, which disrupts the flow of water and nutrients. The ash trees often die within two to four years of an infestation.

Cities across Iowa have wrestled with whether to preemptively cut down some of the trees or to inoculate them with insecticides to save them.

“We haven’t finalized what we’re going to do,” said Jack Wardell, director of Parks and Recreation for Carroll. “It’s sad. We hate to lose any trees, but we knew it was coming.”

City workers have felled up to 15 ash trees that were already severely damaged by ice and wind storms, he said. There are more than 570 ash trees along city streets, in city parks and at the municipal golf course and cemetery.

Wardell’s staff is in the process of evaluating the condition of the trees that have less-severe damage from storms to see if they’re viable or should be cut down. The fewer the ash trees, the fewer the beetles.

City leaders are discussing whether to treat some ash trees — perhaps about 10 percent of the total — with pesticides to protect them. Wardell said the cost is between $100 and $300 per tree, depending on its size. The treatments are required about every two years.

Wardell expects to have a plan for the trees in the next three months.

At Swan Lake State Park, there are more than 530 ash trees that county conservation workers have been monitoring for signs of emerald ash borer damage, said Jason Christensen, director of the county’s conservation department.

“We are not hitting the panic button just yet,” he said. “We will focus our attention on areas in the parks that people use most frequently, which would be campgrounds and the areas we keep mowed that people use for various park activities.”

The beetles can fly for miles after they mature and mate to lay eggs on other ash trees.