Bark Beetles Attracted to Storm Damaged Trees

Spring 2016

Recent history seems to indicate that we are experiencing more windstorms with greater frequency and intensity. Most of us recall the back-to-back windstorms that occurred in July and August 2014. They resulted in road closures, power outages, building damage and many downed trees, in both urban and wildland forests. Another doozy of a storm blew through the region in November 2015, causing human injuries and fatalities as well as property and forest damage. And sandwiched between these major events, localized minor storms with more winds caused noticeable damage.

As forest owners and foresters we well understand the cause and effect relationship between downed trees and bark beetles. Downed or damaged trees at the wrong time of year will attract bark beetles. This is especially true with ponderosa or lodgepole pine (pine engraver beetle) and Douglas-fir (Douglas-fir beetle). The beetles attack the downed trees, limbs and stems three inches and larger in diameter, go through a life cycle under the bark, and a second generation emerges to attack nearby live trees. In the case of the pine engraver beetle (also referred to as Ips because of its genus name), this second generation flight takes place the same summer as the original attack. For Douglas-fir the follow-up attack on live trees occurs in the next year.

Though tree damage was significant, the 2014 storms were, for the most part, late enough in the summer that bark beetle flights had already occurred for the season. Moreover, the moist tissue underneath the bark that harbors bark beetles had sufficiently dried prior to the flights in the spring and early summer of 2015, so we avoided the double whammy of a bark beetle outbreak.

But this will likely not be the case following the November 2015 windstorm. Downed trees, broken tops and fresh cut logs will likely attract bark beetles when they begin to fly in a month or two. The best advice if you have damaged or downed trees is to clean-up as quickly as possible, especially pine species. Unfortunately, the shortened winter logging season did not provide much of an opportunity for salvage harvesting for those with downed merchantable timber.

Points to keep in mind:
• Pine species should be cleaned up this spring. You have until next spring to clean up Douglas-fir.
• Salvage merchantable timber if possible.
• If you cut firewood, get the individual pieces out in direct sunlight to speed drying.
• If possible, remove some or all of the bark.
• Do not stack firewood against live trees.
• Monitor downed trees for bark beetle attacks when daytime temperatures warm to 70 degrees or above.
• Look for boring frass (small piles of reddish colored sawdust) on logs. This is a sure sign that bark beetles have attacked the tree.
• Pile and burn or chip the unused portions of trees.

Don’t hesitate to contact us if you sustained damage during the latest wind storm or if you have any questions on how to avoid a future problem with bark beetles.  –Bill Love, CF