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The mountain pine beetle (''Dendroctonus ponderosae'') is a species of
bark beetle A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the ...
native to the forests of western
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from
Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
to central
British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
. It has a hard black exoskeleton, and measures approximately , about the size of a grain of rice. In western North America, a recent outbreak of the mountain pine beetle and its microbial associates has affected wide areas of lodgepole pine forest, including more than of forest in British Columbia. The outbreak in the
Rocky Mountain National Park Rocky Mountain National Park is an American national park located approximately northwest of Denver in north-central Colorado, within the Front Range of the Rocky Mountains. The park is situated between the towns of Estes Park to the east and ...
in
Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
began in 1996 and has caused the destruction of millions of acres/hectares of ponderosa and lodgepole pine trees. At the peak of the outbreak in 2009, over were affected. The outbreak then declined due to better environmental conditions and the fact that many vulnerable trees had been already destroyed. Mountain pine
beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s inhabit ponderosa, whitebark, lodgepole, Scots, jack, limber, Rocky Mountain bristlecone, and Great Basin bristlecone pine trees. Normally, these insects play an important role in the life of a forest, attacking old or weakened trees, and speeding development of a younger forest. However, unusually hot, dry summers and mild winters in 2004–2007 throughout the United States and Canada, along with forests filled with mature lodgepole pine, led to an unprecedented epidemic. The outbreak may have been the largest forest insect
blight Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism. Description Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organ ...
seen in
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
since European colonization. Monocultural replanting, and a century of forest fire suppression have 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 A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
es (such as CO2) from the atmosphere. Because of its impact on forestry, the
transcriptome The transcriptome is the set of all RNA transcripts, including coding and non-coding, in an individual or a population of cells. The term can also sometimes be used to refer to all RNAs, or just mRNA, depending on the particular experiment. The t ...
and the
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
of the beetle have been sequenced. It was the second beetle genome to be sequenced.


Tree infestations

Mountain pine beetles affect pine trees by laying eggs under the bark. The beetles introduce blue stain fungus into the sapwood that prevents the tree from repelling and killing the attacking beetles with tree pitch flow. The fungus also blocks water and nutrient transport within the tree. On the tree exterior, this results in popcorn-shaped masses of resin, called "pitch tubes", where the beetles have entered. The joint action of larval feeding and fungal colonization kills the host tree within a few weeks of successful attack (the fungus and feeding by the larvae girdles the tree, cutting off the flow of water and nutrients). In recent years, drought conditions have further weakened trees, making them more vulnerable and unable to defend against attack. When the tree is first attacked, it remains green. Usually within a year of attack, the needles will have turned red. This means the tree is dying or dead, and the beetles have moved to another tree. In three to four years after the attack, very little foliage is left, so the trees appear grey. As beetle populations increase or more trees become stressed because of drought or other causes, the population may quickly increase and spread. Healthy trees are then attacked, and huge areas of mature pine stands may be threatened or killed. Warm summers and mild winters play a role in both insect survival and the continuation and intensification of an outbreak. Adverse weather conditions (such as winter lows of -40°) can reduce the beetle populations and slow the spread, but the insects can recover quickly and resume their attack on otherwise healthy forests.


Life cycle

Beetles develop through four stages:
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
,
larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...
,
pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
and
adult An adult is a human or other animal that has reached full growth. In human context, the term ''adult'' has meanings associated with social and legal concepts. In contrast to a " minor", a legal adult is a person who has attained the age of major ...
. Except for a few days during the summer when adults emerge from brood trees and fly to attack new host trees, all life stages are spent beneath the bark. In low elevation stands and in warm years, mountain pine beetles require one year to complete a generation. At high elevations, where summers are typically cooler, life cycles may vary from one to two years Female beetles initiate attacks. As they chew into the inner bark and phloem, pheromones are released, attracting male and female beetles to the same tree. The attacking beetles produce more pheromones, resulting in a mass attack that overcomes the tree's defenses, and results in attacks on adjacent trees. Natural predators of the mountain pine beetle include certain birds, particularly woodpeckers, and various insects.


Management techniques

Management techniques include harvesting at the leading edges of what is known as "green attack", as well as other techniques that can be used to manage infestations on a smaller scale, including: * Pheromone baiting – is luring beetles into trees 'baited' with a synthetic hormone that mimics the scent of a female beetle. Beetles can then be contained in a single area, where they can more easily be destroyed. * Sanitation harvesting – is removing single infested trees to control the spread of beetle populations to other areas. * Snip and skid – is removing groups of infested trees scattered over a large area. *Controlled, or mosaic, burning – is burning an area where infested trees are concentrated, to reduce high beetle infestations in the area or to help reduce the fire hazard in an area. Controlling wildfires has significantly increased since the 1980s and '90s due to firefighting technology. * Fall and burn – is cutting (felling) and burning beetle-infested trees to prevent the spread of beetle populations to other areas. This is usually done in winter, to reduce the risk of starting forest fires. * Pesticides – Biopesticides such as chitosan have been tested for protection against the mountain pine beetle, and pesticides such as carbaryl,
permethrin Permethrin is a medication and an insecticide. As a medication, it is used to treat scabies and lice. It is applied to the skin as a cream or lotion. As an insecticide, it can be sprayed onto clothing or mosquito nets to kill the insects that t ...
, and bifenthrin are used for smaller area applications. The concept of natural plant defense holds hope for eliminating pine beetle infestation. Beneficial microbial solutions are being researched and developed that work with the plant to activate and enhance its resistance mechanisms against insects and disease. The US Forest Service tested chitosan, a biopesticide, to pre-arm pine trees to defend themselves against MPB. The US Forest Service results show colloidal chitosan elicited a 40% increase in pine resin (P<0.05) in southern pine trees. One milliliter chitosan per 10 gallons water was applied to the ground area within the drip ring of loblolly pine trees. The application was repeated three times from May through September in 2008. The chitosan was responsible for eliciting natural defense responses of increased resin pitch-outs, with the ability to destroy 37% of the pine beetle eggs. Dr. Jim Linden, Microbiologist, Colorado State University, stated the chitosan increased resin pitch-outs to push the mountain pine beetle out of the tree, preventing the MPB from entering the pine tree and spreading blue stain mold. Aggressively searching out, removing, and destroying the brood in infested trees is the best way to slow the spread of mountain pine beetles; however, it may not protect specific trees. Spraying trees to prevent attack is the most effective way to protect a small number of high-value trees from mountain pine beetles. Carbaryl, permethrin and bifenthrin are registered in the United States for use in the prevention of pine beetle infestations. 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 it being very toxic to beneficial insects. Bifenthrin is moderately dangerous to mammals, including humans; it is slightly more toxic to birds and aquatic ecosystems than permethrin, as well as extremely toxic to beneficial insects. Colorado's forests are densely wooded, making them much more susceptible to bark beetle attack. Current legislation is in place to help with the growing beetle problem. Colorado Senators
Mark Udall Mark Emery Udall ( ; born July 18, 1950) is an American politician who served as a United States Senator from Colorado from 2009 to 2015. A member of the Democratic Party, he previously served in the United States House of Representatives, represe ...
and
Michael Bennet Michael Farrand Bennet (born November 28, 1964) is an American attorney, businessman, and politician serving as the senior United States senator from Colorado, a seat he has held since 2009. A member of the Democratic Party, he was appointed t ...
announced that Colorado will receive $30 million of the $40 million being diverted by the U.S. Forest Service to fight the millions of acres of damage caused by the mountain pine beetle in the Rocky Mountain region. Fall and burn is the technique being used in Alberta where there is hope of limiting the outbreak to western Canada, preventing its spread to northern Saskatchewan and further towards eastern Canada where jack pine may be vulnerable as far east as Nova Scotia.


Commercial use of affected trees


Timber quality

Wood from beetle-affected trees retains its commercial usefulness for 8 to 12 years after the tree has died, but its value drops rapidly, for within several months, the escaping moisture blows large checks and cracks from the outer perimeter of the wood deep into the heart of the tree. The remaining moisture escapes more slowly, causing small cracks throughout the timber. This causes difficulties for modern high-output automated sawmill operations and greatly increases the lumber losses and the labor to produce high quality wood products. This so-called 'shelf life' is dependent on a number of factors, including economic and stand site conditions. In areas where it is wetter, the trees tend to rot at the base and fall faster, especially if they are larger. The fungus that is carried by the beetles and kills the trees causes blue staining of the sapwood at the perimeter of the tree, but it does not affect the wood's strength, nor are there any harmful human health effects. Blue stain is, however, considered to be a defect in the lumber grading standards and thus is considered a 'down-grade' resulting in a lower commodity market price. All these factors have severely limited the production of blue-stain wood products.


Timber uses

The timber can be used for any wood product from standard framing lumber to engineered wood products, such as glue-laminated products and cross-laminated panels. The epidemic in British Columbia is also creating opportunities for the emerging bio-energy industry. Though there are many small wood working and craft shops that are making furniture and crafts out of the exotic appearing blue-stained wood, and despite the massive supply and the increasingly apparent need to utilize this dead timber, there are very few companies that have created product lines that require large volumes of dead trees. This is largely due to the significant difficulties and increased expense inherent to processing dead timber, and the correspondingly lowered profitability. Blue-stained pine is now available at some big box stores like
Lowe's Lowe's Companies, Inc. (), often shortened to Lowe's, is an American retail company specializing in home improvement. Headquartered in Mooresville, North Carolina, the company operates a chain of retail stores in the United States and Canada. A ...
.


Biofuel/alternative energy production from beetle-killed trees

There has been concern that the huge number of beetle-killed trees may pose a risk of devastating forest fires. Forest thinning to mitigate fire danger is expensive and resource-intensive. Attention is turning to ways to turn this liability into a source of cellulosic ethanol. Leaders in western U.S. states and Canadian provinces have promoted legislation to provide incentives for companies using beetle-killed trees for biofuel or biopower applications. Sellable commodities resulting from MPB damage can help subsidize the cost of forest thinning projects and support new job markets. Colorado's Department of Energy recently provided $30 million toward construction of the state's first cellulosic ethanol plant, to convert beetle kill into ethanol. Lignin, a byproduct of the process, can be sold for applications in lubricants and other goods.


Fire hazards

The long-held belief that beetle infestations and resulting deadkill lead to more devastating forest fires is currently being challenged. Although some disagree, ongoing NASA studies have shown beetle kill may actually reduce available small fuels and consequently limit the effect and reach of fires.


Current outbreak

The current outbreak of mountain pine beetles is ten times larger than previous outbreaks. Huge swaths of central
British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
(BC) and parts of Alberta have been hit badly, with over of BC's forests affected. Under the presumption that the large areas of dead pine stands represent a potential fire hazard, the BC government is directing fuel management activities in beetle areas as recommended in the 2003 Firestorm Provincial Review. Harvesting affected stands aids fire management by removing the presumed hazard and breaking the continuity of the fuels. These fuel management treatments are specifically designed to reduce interface fire threats to communities and Native Americans located in the infestation zone. The interface is the area where urban development and wilderness meet. As of May 2013, the Pine Beetle is aggressively devastating forests in all 19 US-American western states and Canada, destroying approximately 88 million acres of timber at a 70–90% kill rate. Over 13,000 miles of power lines are being endangered with falling trees that increasingly raise the risk of fires that could cause widespread problems for millions of people. The mountain pine beetle has affected more than of trail, of road and of developed recreation sites over in
Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
and southeastern
Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...
; other outbreaks encompass the
Black Hills The Black Hills ( lkt, Ȟe Sápa; chy, Moʼȯhta-voʼhonáaeva; hid, awaxaawi shiibisha) is an isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, United States. Black Elk P ...
of South Dakota and extend as far south as
Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
, and as far north as Montana and Idaho. The US Forest Service is working on a hazard tree removal strategy, prioritizing high-use recreation areas, such as campgrounds, roads and National Forest Service lands adjacent to vulnerable public infrastructures such as power lines and near communities. Image:Pine beetle pitch tube.jpg, A lodgepole pine tree with a pitch tube Image:Yoho National Park of Canada.jpg, Invaded pine tree forest on the slopes of
Chancellor Peak Chancellor Peak is a mountain summit located in Yoho National Park, in the Canadian Rockies of British Columbia, Canada. Its nearest higher peak is Mount Vaux, to the north-northwest. Both are part of the Ottertail Range. Chancellor Peak is a ...
in Yoho National Park,
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
Image:Beetle kill forest colorado.jpg, A pine tree forest north of
Breckenridge, CO The Town of Breckenridge is the home rule municipality that is the county seat and the most populous municipality of Summit County, Colorado, United States. The town population was 5,078 at the 2020 United States Census. Breckenridge is the pr ...
shows infestation in 2008. Image:Pine Beetle in Manning Park.jpg, Pine beetle damage in
E. C. Manning Provincial Park E.C. Manning Provincial Park is a provincial park in British Columbia, Canada. It is usually referred to as Manning Park, although that nomenclature is also used to refer to the resort and Gibson Pass Ski Area, ski area at the park's core. The pa ...
,
British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
,
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, as of August 2010 Image:Mountain pine beetle damage in Rocky Mountain National Park.jpg, Mountain pine beetle damage in
Rocky Mountain National Park Rocky Mountain National Park is an American national park located approximately northwest of Denver in north-central Colorado, within the Front Range of the Rocky Mountains. The park is situated between the towns of Estes Park to the east and ...
as of January 2012 Image:Beetle Infestation Hume Lake, California.jpg, Mountain pine beetle damage at
Hume Lake Hume Lake is a reservoir in the Sierra Nevada, within Sequoia National Forest and Fresno County, central California. Hume Lake is on Tenmile Creek, which is a tributary of the Kings River, and adjacent to the unincorporated community of Hume ...
,
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
as of April 2016
Previously, cold spells had killed off
bark beetle A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the ...
s which are now attacking the forests. The longer breeding season is another factor encouraging beetle proliferation. The combination of warmer weather, attack by beetles, and mismanagement during past years has led to a substantial increase in the severity of forest fires in Montana. According to a study done for the U.S. Environmental Protection Agency by the Harvard School of Engineering and Applied Science, portions of Montana will experience a 200% increase in area burned by wildland fires, and an 80% increase in air pollution from those fires.


Effect on the carbon cycle

Researchers from the Canadian Forest Service have studied the relationship between the
carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere, atmosphere of the Earth. Carbon is the main component of biological compounds as well as ...
and forest fires, logging and tree deaths. They concluded by 2020, the pine beetle outbreak will have released 270 megatonnes of
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
into the
atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
from Canadian forests. There is yet to be an accepted study of the
carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
cycle effect over a future period of time for North American forests, but scientists believe we are at a 'tipping point' of our Western Forests becoming a source of carbon off-put that is greater than that of a ' carbon sink'. Other scientists say that this "tipping point" will reverse itself as new forest life is established. This new growth will remove more carbon dioxide than the mature trees they are replacing would have. According to a 2016 study from the Pacific Institute for Climate Solutions rising levels of carbon dioxide may cancel out the pine beetle impact in British Columbia by 2020. The fertilization effect of the increased CO2 levels has returned BC forests to a carbon sink as of 2016 per Werner Kurz of the Canadian Forest Service.


Effect on water resources

Hydrologists from the
University of Colorado The University of Colorado (CU) is a system of public universities in Colorado. It consists of four institutions: University of Colorado Boulder, University of Colorado Colorado Springs, University of Colorado Denver, and the University of Co ...
have investigated the impacts of beetle-infested forests on the
water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly cons ...
, in particular, snow accumulation and melt. They concluded that dead forests will accumulate more snowpack as a result of thinner tree canopies and decreased snow
sublimation Sublimation or sublimate may refer to: * ''Sublimation'' (album), by Canvas Solaris, 2004 * Sublimation (phase transition), directly from the solid to the gas phase * Sublimation (psychology), a mature type of defense mechanism * Sublimate of mer ...
. These thinned canopies also cause faster
snowmelt In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many part ...
by allowing more sunlight through to the forest floor and lowering the snowpack albedo, as a result of needle litter on the snow surface. Augmented snowpack coupled with dead trees that no longer transpire will likely lead to more available water.


See also

*
Beetle kill in Colorado The mountain pine beetle has killed large numbers of the lodgepole pine trees in the northern mountains of the US state of Colorado. The more recent outbreak of another bark beetle pest, the spruce beetle, is threatening higher-elevation forests of ...
*
Rocky Mountain bark beetle infestation The current bark beetle infestation in the Rocky Mountain region of the United States was first detected in 1996. It involved the Mountain pine beetle, which has since spread across millions of acres of dense forest land. In addition, Spruce beetle ...
* Biopesticide * Chitosan *
Global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
*
United States Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...


References


External links


Death and Rebirth, Mountain Pine Beetle, Pesticides, Carcinogens, Cancer -David Chernoff, Manual For Living
* ttp://www.ext.colostate.edu/pubs/insect/05528.html Trees targeted by beetlebr>Canada's Forests Beetle Attack - The EconomistDeaths of trees 'catastrophic' - Rocky Mountain News
* ttps://web.archive.org/web/20170103042605/https://www.for.gov.bc.ca/hfd/library/lib_MPB.htm British Columbia Ministry of Forests and Range Library - Bibliography of Mountain Pine Beetle Publicationsbr>British Columbia Forestry Ministry - Mountain Pine Beetle Action Plan, information and FAQ
* ttps://web.archive.org/web/20120925005411/http://www.for.gov.bc.ca/hfp/mountain_pine_beetle/2006_IBM.pdf Provincial aerial survey of MPB 2006br>Canadian Forest Service (CFS) Graph and Table showing Mountain Pine Beetle dataThe TRIA Project: Mountain Pine Beetle System Genomics
DIE {{DEFAULTSORT:Mountain Pine Beetle Beetles described in 1902 Beetles of North America Climate change in Canada Scolytinae Effects of climate change Environmental disasters in Canada Insect pests of temperate forests Woodboring beetles Articles containing video clips Environmental issues in Alberta