Emerald Ash Borer Detected in All WI Counties News | July 27, 2024 | 0 | by Morgan McCarthy Wisconsin is being infested by tree-killing beetles. The state Department of Natural Resources confirmed on Friday that the emerald ash borer has been detected in Burnett County, meaning the infestation has now spread to all 72 counties. The pest is called an emerald ash borer because the green beetle bores its way into ash trees, eventually killing the trees. The department says the insect is expected to kill 99 percent of Wisconsin’s white, black and green ash trees.