The mountain pine beetle (MPB), Dendroctonus ponderosae, is a species of bark beetle native to the forests of western North America from Mexico to central British Columbia. It has a hard black exoskeleton and measures about 5 millimetres, about the size of a grain of rice.

Mountain pine beetles inhabit pines, particularly the Ponderosa Pine, Lodgepole Pine, Whitebark Pine, Scots Pine and Limber Pine. The bristlecone pines and pinyon pines are less commonly attacked. During early stages of an outbreak, attacks are limited largely to trees under stress from injury, poor site conditions, fire damage, overcrowding, root disease or old age. As beetle populations increase, the beetles attack the largest trees in the outbreak area.

Tree infestations

The beetles kill the trees by boring through the bark into the phloem layer on which they feed and in which eggs are laid. Pioneer female beetles initiate attacks, and produce pheromones which attract other beetles and results in mass attack. The trees respond to attack by increasing their resin output in order to discourage or kill the beetles. It isn't the number of pitch-out tubes that kill the pine tree but the beetles carry blue stain fungi which, if established, will block the tree resin response. Over time (usually within 2 weeks of attack), the trees are overwhelmed as the phloem layer is damaged enough to cut off the flow of water and nutrients. In the end, the trees starve to death, and the damage can be easily seen from the air in the form of reddened needles. Entire groves of trees after an outbreak will appear reddish for this reason. Usually, the older trees die first. After particularly long and hot summers, the mountain pine beetle population can increase dramatically, which leads to the deforestation of large areas. Current outbreaks are in Rocky Mountain National Park.^[1]

Integrated Pest Management (IPM)

There are some natural IPM defenses against the MPB. Owners nail to a tree an “anti-aggregation pheromone” in a small packet, which mimics the chemical scent given off by beetles when a tree is full of insects. It can work when beetles are not too numerous, but at some point the beetles are not deterred.^[2]

The US Forest Service tested chitosan^[3][4], a eco-friendly biopesticide, to pre-arm pine trees to defend themselves against MPB. The US Forest Service results show AgriHouse's EPA registered ODC Collodial Chitosan elicited a 40% increase in pine resin (P<0.05) in Southern Pine Trees. The US Forest Service applied 1 ml ODC chitosan in 10 gallons water to the ground area within the drip ring of the loblolly pine tree. The ODC chitosan application was repeated three times from May through September in 2008. The ODC chitosan was responsible for eliciting natural defense responses of increased resin pitch-outs with the ability to destroy 37% of the pine beetle eggs.^[5] Dr. Jim Linden, Microbiologist, Colorado State University, states that the chitosan increased resin pitch-outs push the boring pine beetle out of the tree, preventing the MPB from entering the pine tree and spreading blue stain mold.^[6]

The most effective way to manage pine beetles is to use the integrated pest management strategy (IPM). The strategy includes removing and cutting dead trees as well as thinning trees to maintain a healthy forest. Spraying is helpful in smaller scale situations where a few high value trees wish to be saved. Verbenone, which is an anti-aggregate pheromone, can also be used in smaller scale operations when spraying is not an option.^[7]

The best and only long run defense from mountain pine beetles is to maintain a healthy forest. Cutting and thinning of trees as well as an age and species diversification is most helpful. This also helps to prevent hazardous forest fires.

Spraying is one of the more effective ways of protecting a pine tree from beetles. The spray is made up of Carbaryl (Sevin SL and XLR, and others), Permethrin (Astro, Dragnet and others) and, bifenthrin (Onyx). Carbaryl is considered by the EPA to likely be carcinogenic to humans. It is moderately toxic to wild birds and partially to highly toxic to aquatic organisms. Permethrin is easily metabolized in mammalian livers so is less dangerous to humans. Birds are also practically not affected by permethrin. Negative effects can be seen in aquatic ecosystems as well as very toxic to other beneficial insects. Bifenthrin is moderately dangerous to humans and mammals. Bifenthrin is slightly more toxic to birds and aquatic ecosystems then permethrin, as well as extremely toxic to other beneficial insects.^[8]

Spraying is very effective at protecting the pines but is not recommended for large-scale use due to financial and ecological reasons. Pines should be sprayed before the beetle flight in July, so May or June will yield the best results. You can spray your own trees but this requires a great deal of spraying equipment and safety equipment. A licensed applicator is highly recommended.^[9]

Verbenone is the main compound for the anti-aggregate pheromone for the mountain pine beetle. This compound is produced by 3 companies: Contech, Synergy Semiochemicals Coorp, and Hercon Environmental. Verbenone is a behavior modifying pheromone that tricks the pine beetle into believing that the tree is no longer useful to more beetles and they will leave the tree alone. Verbenone is useful in campsites and places close to creeks and rivers where spraying cannot be used. Verbenone does not kill the insects it simply pushes them away to another tree or area. It has been pretty successful in areas with low beetle populations but has not been very successful in areas with higher populations. Verbenone is only useful in small-scale operations.^[10]

Logs that are infested with beetle larva may be dealt with by burning, burying, chipping. They can also be dealt with using solar treatment.^[11] The solar treatment for killing pine beetle larva involves cutting and heating the logs containing the larva to 110 degrees F in or to kill the larva. There are 2 options when using solar treatment, with plastic and without plastic. This method takes 8 weeks and should be performed from mid April until early May, before the beetle flight. Logs with plastic cover will work better in slightly cooler climates. This method works well with a small number of logs in a high valued area.^[12]

Life cycle

Mountain pine beetle damage (brown trees) to pines south of Field, British Columbia, Canada.

Approximately two weeks following oviposition, pine beetles hatch as white larvae. They dig into tree bark where they spend the winter, then grow up to 7 mm long in the spring. The pupal stage ends in the late spring or early summer, and from mid-July to mid-August, the beetles leave their tunnels and fly to new trees. Female beetles release pheromones to attract males and encourage mass attacks.^[13] The lifespan of a single pine beetle is about one year.^[14]

Temperatures down to −30 °C to −40 °C (−22 °F to −40 °F) for at least several days, or at least twelve hours of −40 or lower, kills most mountain pine beetles.

Current outbreak

The current outbreak of mountain pine beetles is ten times larger than previous outbreaks.^[15] In Wyoming and Colorado in 2006 there were 1 million acres (4,000 km²) of dead trees. In 2007 it was 1,500,000 acres (6,100 km²). In 2008 it is expected to total over 2 million acres (8,100 km²).^[16] It may be the largest forest insect blight ever seen in North America.^[17] Climate change has contributed to the size and severity of the outbreak , and the outbreak itself may, with similar infestations, have significant effects on the capability of northern forests to remove greenhouse gas from the atmosphere.^[18] Huge parts of central British Columbia along with parts of the forests of Alberta have been hit badly. The recently mild winters have British Columbia's forestry officials worried because the beetles will have a devastating impact on an ecosystem which may be ill-equipped naturally to deal with it. Fortunately, if properly contained, the pine beetle can be burnt out, but such containment is prevented during cases in which the infection has towns, homes, and cities completely surrounded. A cold snap in early 2008 was hoped to have dropped the pine beetle population to more manageable levels.^[19] However, preliminary results from the summer of 2008 indicate that the cold winter was less successful at killing pine beetle than predicted.

As of 2008, there was also a large outbreak in Colorado. The largest problem in the eradication of the beetle is that homes in the area are close to the infected trees, so that a controlled burn could be problematic. Furthermore, since the trees that are being hit are older and the Ponderosa Pines affected are stimulated to spread seeds by heat of around 130 degrees from either fire or solar radiation much forest will die before it is renewed.

A lodgepole pine tree with a pitch tube.

A lodgepole pine tree infested by the mountain pine beetle, with visible pitch tubes.

Invaded pine tree forest on the slopes of Chancellor Peak in Yoho National Park, Canada

A pine tree forest north of Breckenridge, CO showing infestation in 2008

Effect on carbon cycle

Researchers from the Canadian Forest Service have studied the relationship between the carbon cycle and forest fires, logging and tree deaths. They concluded that by 2020 the pine beetle outbreak will have released 270 megatonnes of carbon dioxide into the atmosphere from Canadian forests. There is yet to be an accepted study of the carbon cycle effect over a future period of time for North American forests.^[15]

See also

• Biopesticide
• Chitosan
• Community Economic Diversification Initiative (CEDI) an important component of Federal Mountain Pine Beetle (MPB) Program provided by Western Economic Diversification Canada
• US Forest Service

References

Wikispecies has information related to: Mountain pine beetle

Wikimedia Commons has media related to: Dendroctonus ponderosae

• The Falldown Documentary- A look at the devastating impact of the beetle on British Columbia and Canada's Economy
• BC Pine Beetle Information Portal
• Canada's Forests Beetle Attack - The Economist
• Rocky Nat'l Park Fights Pine Beetles With Burner - CBS4Denver
• Deaths of trees 'catastrophic' - Rocky Mountain News
• Pherotech International, Mountain Pine Beetle and other Bark Beetle controls through use of Integrated Pest Management Plans
• Washington Post article: 'Rapid Warming' Spreads Havoc in Canada's Forests
• Natural Resources Canada site on the Mountain Pine Beetle
• Rocky Mountain pine beetle epidemic devastating to Colorado forests
• Detailed information from Alberta Forest Health about the mountain pine beetle's life cycle and what to look for in beetle infestations
• British Columbia Ministry of Forests and Range Library - Bibliography of Mountain Pine Beetle Publications
• British Columbia Forestry Ministry - Mountain Pine Beetle Action Plan, information and FAQ
• David Suzuki Foundation - Call for ecosystem-based management
• British Columbia Ministry of the Environment Mountain Pine Beetle FAQ
• BC MPB outbreak projection update w/ 2005 data
• Provincial aerial survey of MPB 2006
• Map of projected percentage of pine killed in British Columbia by 2012
• Genomics project on the three interacting organisms (beetle, fungus, and tree)
• Grande Alberta Economic Region's Mountain Pine Beetle pages
• Towards Transformation: The Economic, Social and Environmental Costs of the Mountain Pine Beetle in the Grande Alberta Economic Region
• Flickr MPB image pool
• The TRIA Project: Mountain Pine Beetle System Genomics
• DISPOSAL OF TREES AFFECTED BY THE PINE BEETLE: THE DILEMMA AND WHY AIR CURTAIN BURNERS SHOULD BE USED
• Non-profit organization, working in conjunction with universities, to develop new technologies using pine beetle kill for reclamation and energy needs