Some of the most important pests of our forests are wood boring beetles. Most beetles that bore into trees do not feed on the wood. The beetles transport fungi that grow on the walls of the tunnels and use the fungus as their source of food.
Several beetle infestations are causing widespread damage to forests in different areas of North America. The Mountain Pine Beetle has been increasing in numbers in many parts of western North America over the past 15 years. Mountain Pine Beetle carries the blue stain fungus that is responsible for the loss of many trees. The fungus invades and clogs the vascular system of the tree, disrupting water and nutrient transport. The needles turn red and the tree dies within a year. The primary trees affected are the lodgepole pines, but other species can be hosts. Last year, Mountain Pine Beetle devastated over 500,000 acres of trees in 2010 and over 4 million acres since 1996 in Wyoming and Colorado.
What is behind the beetle outbreaks? Contributing factors are warmer temperatures during the winter months that are not cold enough to reduce beetle populations by killing the overwintering beetles, and drought conditions that stress the trees and make them easier for the beetles to colonize. Disturbance of the forests by fire, harvesting or other factors that would create diversity in the age and the species of trees has been lacking. The susceptible forests are packed with dense stands of trees most of them at an age that is susceptible to the bark beetle. The confluence of factors has created a favorable environment for beetle populations to build to record levels and cause record destruction.
Efforts to contain the beetle spread in Canada have included the harvest of infested trees. Some of the Canadian lumber is making its way to market and stirring trade issues with the US. Alberta Province is spending 15 Million Canadian Dollars to remove over 170,000 trees in hopes of saving an estimated 1.7 million trees from future infestation.
Dead trees are a potential hazard to people, cars and utilities. Campers in the Colorado Rockies should evaluate parking areas and campsites. Areas within falling distance of red-colored pine trees should be avoided. The dying trees are more susceptible to toppling especially during high winds. What can be done about the beetle? At this point, not much. Individual trees of high value in urban areas can be protected, but the beetle infestation is too large to contain. The good news is that the Mountain Pine Beetle does not destroy forests, it only changes their composition. The result of the current population explosion will be the death of many older trees and their replacement by younger trees.
Mountain Pine Beetle
Photo: Dion Manastyrski, B.C Ministry of Forests and Range
Dead and Dying (Due to Mountain Pine Beetle) Lodgepole Pine
Photo: US National Forest Service
Living With Insects Blog 
As a hiker, seeing an abundance of brown, dying evergreens among healthy trees can be disturbing. I’ve seen the effects of fire on a forest firsthand, but I think the devastation caused by borer beetles is even worse. Fires are necessary to clear underbrush and old growth. I don’t see anything that redeems invasive borers though. (I’m aware that this may be an ignorant statement. Perhaps something necessary and useful -does- come from borers’ work that I don’t know about.) When I see a few dying trees in state parks, I acknowledge that the process of growth and decay is a natural one. However, seeing a host of dying trees peppering the horizon is irritating, especially when I think that it’s damage that could have been prevented had we known sooner of the potential dangers brought on by a global market. In the very least, though, it’s a relief to know there are decent pesticides that can ward off some of these beetles. On the other hand, you still have to take into account the rate at which any borer species may grow accustomed to the pesticide and become impervious to it.
Actually, Mountain Pine Beetle is a native species. The balance has shifted to conditions that favor MPB outbreaks, due to shifts in climate. Once insects bore into a tree, they are very difficult to kill with insecticides. Some of the new systemics can work, but they are very expensive to apply and cost prohibitive over 10s or 100s of thousands of acres. Cutting infested trees and exposing the logs to sunlight will kill most of the beetles in an infested tree. This method is time consuming, but effective.
I will post later about some of the invasive species that are affecting forests.
The last image really says it all. Almost half the trees in the image were dead and dying! I have no idea it’s so bad!
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