If you see “D” shaped holes in your ash tree, the emerald ash borer (Agrilus planipennis) may just be your new neighbor. “The emerald ash borer (EAB) is an invasive, green metallic beetle that came over from Asia,” said Carbondale town arborist Carl Meinecke. “It’s been on the Front Range of Colorado for about 10 years.”
It is difficult to know how many trees have been felled in the U.S. by this half-inch long green bug but it’s safe to say the number is in the hundreds of millions.
The EAB was first detected in Detroit in 2002 and has been making fast tracks. If you look at the interactive U.S. Department of Agriculture map that documents the spread of the EAB per county, you’ll see that the bug has eaten its way through a smorgasbord of states from the northern tip of Maine, south through Tennessee and dipping into Georgia, South Carolina, Alabama and Louisiana. The beetles have traveled through Ohio, Indiana, Illinois, Michigan, Minnesota, Iowa, Missouri and Arkansas, inching tree by tree, into Oklahoma and Texas. They are coming across Nebraska and Kansas and set up camp on the Front Range in 2013. EABs also inhabit trees in a tiny spot in northwestern Oregon.
Garfield County is on that map, all because of Carbondale. The beetle has not yet been confirmed anywhere else on the West Slope. “Probably somebody on the Front Range had a tree that died from EAB,” said Meinecke. “Then, they took it down themselves, cut it up into firewood, maybe threw it in a truck and came to Carbondale to visit or something.”
According to most reports, that’s how humans help the EAB travel long distances. Meinecke said he put some samples from local ash trees suspected of infestation in his office. “And a couple of weeks later, bugs actually started emerging in my office and were crawling around,” he said — a sort of Trojan Horse move on the part of the EABs. “They weren’t coming out when I took the samples.”
Carbondale has 400 ash trees, said Meinecke, who confirmed the presence of EABs in the summer of 2023. He developed a management plan for the trees that September, which includes tree trunk injections of emamectin benzoate, pruning and taking out infested trees if necessary. “We decided to go with the tree injection,” he said. “It has the least amount of risk to pollinators and things around it.” Biological pest controls — bugs that kill other bugs — are not an option. “I know the City of Boulder has been experimenting with a few types of parasitic wasps,” he said, “but at this time it is not readily available.”
Meinecke has completed some assessments and identified trees that will be treated or removed. “Trees that have been selected for treatment have a blue dot at their base,” he said. Two hundred twenty trees will be treated on a three-year rotation in River Valley Ranch and in Town, and 210 will be removed over time.
Signs of infestation
Clear signs of EAB presence include increased woodpecker activity, “S” shaped patterns (called “galleries”) under the bark, vertical splits or loss of bark, sparse leaves or branches in the upper part of the tree, new sprouts below an infestation site and those “D” shaped holes where the adults exit the tree.
The EAB is dormant from September through April, during which time pruning or tree removal is recommended. The bug’s active period is from May through August when any cutting is discouraged. “That’s when adult EABs are flying,” explained Meinecke. Moving ash firewood is prohibited. Burning ash wood is allowed only where the tree came down and in compliance with fire restrictions.
Arbor Day presentation
Meinecke encourages everyone to celebrate Arbor Day on Saturday, May 4 at Colorado Meadows Park at 10am. He will demonstrate how to plant a tree and talk about the upcoming update to the Town tree inventory. “I need about five volunteers to help me with the inventory,” he said.
Private property owners with concerns about ash trees can contact Carl Meinecke at cmeinecke@carbondaleco.net or a tree care professional who is certified and licensed for ash tree treatment or removal.