I just returned from a trip to the Black Hills in South Dakota. While Mount Rushmore was impressive, the amount of dead trees in the otherwise beautiful forests was depressing. They were everywhere. In addition, there were huge slash piles stacked in the forest. It was ugly and sad to see the extent of the damage.
We wondered what had killed so many trees. They weren’t burned. I thought maybe a windstorm of epic proportions had occurred. Yes, they do get big winds that did knock over many dead trees. But it wasn’t the wind that killed the trees. It was mountain pine beetles.
At Mount Rushmore, there was an exhibit with a detailed video on the damage these native bark beetles are doing to trees all over the West and into Canada. Colorado has had 3.4 million acres of forests impacted from 1996 to 2013 (Colorado State Forest Service, 2016). British Columbia forests have been decimated losing over 44 million acres of pine trees. Allan Carroll, an insect ecologist at the University of British Columbia, expects the beetles to spread across the continent to Nova Scotia and down into the Midwest and New England (National Geographic, 2015). Trees in the Sierra have been impacted.
Bark beetles are part of the natural processes in a forest. However, with warmer winters, they aren’t being killed off, so populations have exploded. Combine that with the drought conditions across the West that have stressed trees and we have forests highly susceptible to bark beetle attack. Additional contributing factors to susceptibility to bark beetle infestation include large numbers of old trees, overcrowding and poor growing conditions.
Once a tree is infested with bark beetles, particularly under forest conditions, nothing practical can be done to save the tree. Although woodpeckers and various insects prey on mountain pine beetles, under epidemic populations these natural predators can’t keep up with the numbers of beetles. There are no pesticides labeled for use on mountain pine beetle. Logging or prescribed burns can slow the spread of the beetles, but these tactics are often met with understandable resistance.
The best thing for a homeowner with individual trees to do is to keep trees healthy. Water all year long, including through the winter. Avoid damaging trees with mowers, or other equipment. Don’t park under trees; it damages roots. Prune only after a hard freeze to avoid attracting beetles to fresh cuts.
For more information go to Nevada Division of Forestry: http://forestry.nv.gov/forestry-resources/forest-health/mountain-pine-beetle/.
JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at skellyj@unce.unr.edu.
