Sawyers take over 3000 acres of trees in BWCA

Photo of Sawyers on tree in bwca

What? You thought sawyers weren't allowed in the BWCA? Think again. Nature doesn't follow the same rules that humans do. Besides, the sawyers we are talking about aren't human, they're insects called long-horned wood borers (Monochamus spp.). During the aerial survey flown this past summer, 3400 acres of jack pine stands with mortality due to wood borers were mapped around the Gunfllint Trail corridor in Cook Co.

map of sawyers in cook county in 2003

We usually think of wood borers infesting trees that have already been killed by something else, like drought, fires, wind or bark beetles. Kamal Gandhi, a graduate student at the U of MN studying insects following the 1999 blow down in the BWCA, has found otherwise. She found up to 100% mortality of jack pine on her plots due to wood borer attack. Apparently the wood borer populations built up in the downed pine trees over the last few years and were then able to attack and kill standing live jack pine. She observed large numbers of female wood borers ovipositing on standing live jack pine in blow down areas. Older larvae bore into the wood but younger larvae mine in the cambium layer. When there are enough young larvae present in a live tree, the vascular system can be cut off, just like the effect of bark beetles. So, now you know that mass attack by sawyer larvae can kill living pines, too.