Managing pine bark beetle damage

Quick facts

  • Bark beetles are associated with pole-sized and mature red pine forests.
  • Outbreaks are commonly observed during drought years.
  • Thinning is one tool that reduces competition and lowers the likelihood of bark beetle outbreaks.
  • Time thinning and other forestry operations to occur during the fall and winter months when bark beetles are not active.
  • Thinning should not occur during a drought and for one year following a drought. 
  • Operators should avoid wounding trees during thinning and harvesting operations.

  • Consult a forestry professional to determine the appropriate time of year to conduct thinning operations to minimize bark beetle damage.

Close up side view of pine bark beetle
Pine engraver beetle, a native pine bark beetle in Minnesota

Pine bark beetles (including the pine engraver species Ips pini and Ips grandicollis) are responsible for killing many pine trees in Minnesota.

Minnesota’s red pines are a commercially and ecologically important species throughout the state. Pine engraver beetles are commonly associated with pole-sized (21 to 50 years) and mature red pine forests (older than 50 years).

According to Minnesota Department of Natural Resources annual reports, bark beetles impacted 4,891 and 3,150 acres of pine forests in the state in 2014 and 2015, respectively. Actual acreage is difficult to determine since bark beetle activity occurs in variable-sized pockets. Outbreaks are commonly observed during drought years.

Beetles develop tunnels beneath the bark, which reduces the flow of water in the tree, ultimately contributing to death in an unhealthy tree.

Notable bark beetle outbreaks associated with drought years in Minnesota

Drought year(s) Notes from MNDNR forest health reports
1976-1977 On sandy soils, conifers of all ages died or were weakened to the point where bark beetles became a problem.
1987-1988 A large number of bark beetle pockets were initiated in 1987. Four generations of bark beetles were bred in 1988. Eighty percent of all pine plantations in Stearns, Benton, Sherburne, Kanabec, and Anoka counties had active bark beetle pockets in 1988. Weather conditions identified this as a 150-year drought.
2004-2005 In southeastern counties, a significant amount of bark beetle activity was observed in the early summer of 2004.
2006-2009 This serious and prolonged drought created stress conditions favorable for bark beetle build-up. Damage from Ips and Dendroctonus bark beetles totaled 3,600 acres in 2009.
2012 Damage from Ips bark beetles totaled 310 acres, but adequate rainfall occurred in the central portion of the state to minimize activity.
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Matthew Russell, Extension forester; and Jeffrey Hahn, Extension entomologist

Reviewed in 2018

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