The most damaging bark beetle species attacking Minnesota's pines are native engraver beetles (Ips species), also known as pine bark beetles. Red (Norway) and jack pine are the most common victims of pine bark beetles, although white pine and spruce can also be infested. There are several other bark beetle species that inhabit pines, but they are rarely problematic. The management advice applies to these other bark beetle species as well.
Pine bark beetles can quickly kill a few upper-canopy branches and eventually the entire tree. Needles on attacked branches fade from green to yellow-green and then turn completely orange in a matter of weeks.
Fortunately, pine bark beetles prefer to attack stressed pine trees or freshly-cut pine and spruce branches and trunks (called slash), so healthy trees are not usually harmed. Pine bark beetles cannot live in pines with loose bark or pines that have been dead for over a year.
It is not unusual to lose some mature pines in plantations from pine bark beetles occasionally, so the loss of a few stressed trees should not cause concern. In some circumstances, if an area with many pines is damaged by wind, fire, or extreme drought, significant numbers of remaining pines can be attacked and killed by pine bark beetles. Lightning strikes or thinning pines from late winter through summer without promptly removing slash can also promote pine bark beetle attack of the remaining pines.
Pine bark beetles are found throughout Minnesota and are widely distributed in North America.