A swath of Minnesota's forest heavily impacted by eastern larch beetle.
Photo by Marc Roberts, USDA Forest Service.
Eastern larch beetle (ELB) is a native bark beetle infesting tamarack (eastern larch) at unprecedented levels throughout the tree's range.
Adults emerge in late spring and bore into the trunk to feed, mate, and lay eggs. After eggs hatch, larvae tunnel throughout the phloem, creating feeding galleries that eventually cut off water and nutrient flow, killing the tree.
Historically in Minnesota, ELB produced localized outbreaks that lasted only a few years. However, climate change has lengthened the growing season, increasing reproductive success and allowing the beetle population to increase at faster rates than in the past. As of 2017, Minnesota is in its 17th consecutive year of ELB outbreak, and currently has more than 440,000 acres with affected forest tamarack. There is no indication that the outbreak is subsiding.
Eastern larch beetle occurs anywhere tamarack is found across the northern United States and Canada.
Vertical galleries with many perpendicular branches are the identifying characteristics of eastern larch beetle infestation. Infested tamarack often looks reddish in late winter, as woodpeckers remove outer bark to feed on beetle larvae in the reddish inner bark.