With the increase of temperatures due to global warming, mountain pine beetle larvae are now capable of living through winter in areas farther north that were formerly too cold for their survival. In addition, the beetles have moved to higher elevations. The expansion of the mountain pine beetle range due to global warming has resulted in damage to Pinus forests in previously unaffected locations.
Eradication efforts currently in place focus on short-term treatments, such as insecticides, long-term prevention, and landscape restoration. Specifically, larvae hidden beneath the bark are targeted with treatments such as stripping away the bark in order to expose the larvae to harsher environmental conditions. In addition, solar techniques can be used to heat up the phloem of the trees until they reach temperatures unbearable to the beetles. A great deal is being spent on these techniques in order to preserve the forest ecosystems that have been present for so long and that now run the risk of complete destruction.
Once a female adult beetle exits the tree from in which it hatched, it will attack a new tree, meanwhile releasing a pheromone that attracts other beetles to the site. These other beetles are then able to attack the target tree, as well as adjacent trees. Males that have been attracted to these trees then attack and release their own pheromones, thereby attracting more females to the site. Once a critical density of beetles per tree has been reached, males and females then release more pheromones, signaling to others to attack adjacent trees instead.
One of the pheromones produced by female D. ponderosae at critical density is called verbenone. Because verbenone at one site signals to D. ponderosae to avoid that site and seek out another, verbenone has been considered as a repellent the mountain pine beetle.
Communication Channels: acoustic ; chemical
Other Communication Modes: pheromones
Perception Channels: acoustic ; chemical
Dendroctonus ponderosae is not an endangered species, nor does there seem to be any concern about conserving the species as a whole. In fact, due to the nature of D. ponderosae, the focus is shifted more to eradicating the pest and restoring forest ecosystems rather than maintaining the species.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
An adult female mountain pine beetle deposits her eggs in egg galleries within the phloem of a Pinus tree, and the eggs lay dormant for 10-14 days before hatching. Larvae then hatch from the eggs, appearing white with brown heads and no legs. These larvae develop through their instars for approximately ten months. Development time varies, depending on the temperature of the phloem in which the larvae are found; colder phloem results in prolonged development, while warmer phloem can shorten the duration of development. By the time winter arrives, the larvae have reached their third or fourth instar, which are much more durable in cold weather. The instars metabolize glycerol during this time, which prevents them from freezing. At the end of their development, around June of the following year, Dendroctonus ponderosae larvae build oval cells stemming out from their egg gallery. Within the oval cell each individual larva develops into a pupa. This stage is normally complete by the end of June or July. After a month or so this pupa develops into an adult. The adults can feed on bark within reach of their oval cells until they break into other oval cells or penetrate the bark to emerge from the tree. For the beetles infesting Pinus trees, this normally takes place in mid-August. At that point the adult females fly to new Pinus trees, secrete pheromones to attract males, and begin penetrating the tree bark to form new egg galleries. When males arrive, they also secrete pheromones to attract more beetles to the location, then fertilize the females beneath the bark of the Pinus tree. From here, the cycle starts again.
Development - Life Cycle: metamorphosis
Mountain pine beetle infestations cause the destruction of huge numbers of trees. To curb the massive losses due to these infestations, governments in the United States and Canada have supplied large amounts of money toward eradication efforts. Without these efforts or any future change, the death of Pinus trees leads to increased carbon emissions. In addition, the destruction of Pinus forests leads to an increase in wildfire fuel, which could be potentially harmful to humans. Especially significant are the forest fires which occurred in Yellowstone National Park in 1988 and were the result of mountain pine beetle damage to Pinus trees. Deforestation due to mountain pine beetles can also negatively affect local timber industry.
Mountain pine beetles are not known to provide any benefits for humans.
Dendroctonus ponderosae, although considered a parasite and nuisance now, has actually co-evolved with Pinus trees for many years. The forest ecosystem actually began to rely on periodic infestations of mountain pine beetles, and the subsequent clearing due to forest fires. Now, however, predators of mountain pine beetles cannot control their populations. The destruction of Pinus trees affects more than just the trees themselves; animals in the forest ecosystem that rely on the trees for protection and shelter, such as deer and elk, are also affected by tree destruction.
Infestations of Dendroctonus ponderosae occur wherever Pinus trees are, whether they are in forests, on mountains, or isolated in yards. Due to the transportation of firewood, isolated stands of Pinus can become infected. After one tree is infected with mountain pine beetles, nearby trees usually succumb to the infestation as well. Trees inevitably die after infestation with the beetles, due to the catastrophic damage caused by the tissue ingestion of mountain pine beetle larvae as well as the introduction of the blue stain fungus by adult beetles. Blue stain fungus invades the phloem and eventually cuts off nutrient supply in the tree, resulting in tree death. Blue stain fungus, which is distributed by mountain pine beetles alone, stops the tree from using resin to remove the beetles from its phloem. In this way, blue stain fungus and mountain pine beetles are mutualists.
Signs of mountain pine beetle infestation include the presence of pitch tubes on the surface of trees in which the beetles have begun to dig egg galleries. Color of pitch tubes ranges from brown to pink or white. An increased presence of woodpeckers could also indicate Dendroctonus ponderosae infestation, as beetles serve as a valuable food source to the woodpeckers. Sapwood - the younger, outer portion of the tree - could also have blue stains, indicating that beetle infestation has occurred, and that the adult beetles introduced the blue stain fungus. The final sign of mountain pine beetle infestation is the transformation in color of the crown of infested Pinus trees to red or yellow. This is the last visible sign of infestation, as it does not occur until eight to ten months after the initial infestation.
There are some ecologists and landowners that do not necessarily see the damage by mountain pine beetles as totally negative. Ecologists point out that as a result of destruction of portions of Pinus forests, canopy overgrowth decreases, allowing understory vegetation to blossom and expand. This increases the plant diversity, which is beneficial for the forest ecosystem. Some landowners, meanwhile, prefer the growth of plants that normally cannot thrive under a dense canopy of Pinus trees.
Ecosystem Impact: parasite
Species Used as Host:
Mutualist Species:
Commensal/Parasitic Species:
Dendroctonus ponderosae larvae survive mainly on the phloem of the tree which they inhabit. They feed in lines perpendicular to the egg galleries in which they were hatched. Directly after pupation within the oval cells, adults feed on fungal spores that other beetles have introduced into the tree, as well as additional tree tissues. Adults later feed on the bark of the tree as they make their way from the oval cells out into the open.
Plant Foods: wood, bark, or stems; sap or other plant fluids
Other Foods: fungus
Primary Diet: herbivore (Lignivore, Eats sap or other plant foods); mycophage
Dentroctonus ponderosae (the mountain pine beetle) inhabits a large portion of western North America. This species ranges from British Columbia in the north to northern Mexico in the south, as well as from North Dakota west to the Pacific coast. Since D. ponderosae infests Pinus ponderosa, as well as other trees in the genus Pinus, the range of the mountain pine beetle is mostly coincident with that of forests containing these trees.
Biogeographic Regions: nearctic (Native )
Mountain pine beetles infest Pinus trees in western North American forests. While they can reach relatively high altitudes, their preference is for lower altitudes with suitable temperatures. Because instars (stages of larvae) of Dendroctonus ponderosae are susceptible to the cold, the beetles prefer to reside in areas with moderate temperatures. This limits the range of D. ponderosae with respect to both altitude and northern expansion.
With the increase of temperatures due to global warming, mountain pine beetle larvae are now capable of living through winter in areas farther north that were formerly too cold for their survival. In addition, the beetles have moved to higher elevations. The expansion of the mountain pine beetle range due to global warming has resulted in damage to Pinus forests in previously unaffected locations.
Mountain pine beetles preferentially infest trees that are under stresses such as injury or disease, fire damage, old age, and overcrowding. These trees are also the first to die. If the beetle population gets large enough, D. ponderosae will infest healthier Pinus trees in the area. As these trees die as well, entire populations of Pinus trees become kindling for fires that can have drastic effects on the forest ecosystem.
Range elevation: 0 to 3353 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest
The life cycle of Dendroctonus ponderosae lasts approximately one year, but it is highly climate dependent. At higher latitudes or elevations, the colder temperatures lengthen the larval development stages to about two years. Normally the adult stage last only a few days, and consists of leaving the tree in which they developed, flying to a new tree, and reproducing under the bark there.
Range lifespan
Status: wild: 1 to 2 years.
Average lifespan
Status: wild: 1 years.
Average lifespan
Status: wild: 1 years.
Dendroctonus ponderosae is black and cylindrical and, on average, 5 mm long. The gradual curve of the hind wing of the adult D. ponderosae distinguishes it from other bark beetles that normally have sharp spines along the hind wing.
Mountain pine beetle eggs are normally white, while the larvae typically have white bodies and brown heads. The larvae are also legless, as they remain under the bark of the Pinus trees for the duration of their development and have no need for legs.
Range length: 5 to 7.5 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
Woodpeckers (Picidae) are a natural predators of mountain pine beetles, as they penetrate the bark of Pinus trees to feed on adults and larvae. Several other beetles, including two species of checkered beetles (Cleridae) also feed on the adults and larvae beneath the bark. Dolichopodid flies also feed on Dendroctonus ponderosae.
Other predators, however, target Dendroctonus ponderosae as the adults fly from their tree of origin to a new host. These predators include nuthatches (Sitta) and other birds.
Known Predators:
Upon emerging from the oval cell in which they completed development, adult female Dendroctonus ponderosae fly to a Pinus tree that is suitable for breeding and maintaining progeny. Here they build an egg gallery by burrowing straight through the bark of the tree and into its phloem. These females then secrete pheromones in order to attract male D. ponderosae to the site. The males, upon arrival to the site, secrete their own pheromones to attract both male and female beetles to the location, initiating a local infestation.
At this point, the males proceed to exhibit mate selection by preferentially choosing females whose egg galleries are of larger size but within smaller trees. Smaller males are more likely to enter galleries than larger males, most likely because of some kind of size-dependent sexual selection dependent on the females. Large females in turn show sexual selection by allowing larger males to enter their galleries much more quickly than smaller males. To enter the galleries, males must first stridulate (rub their legs together in order to produce a certain sound). Once a female grants access to the male, the male enters the gallery and fertilization occurs. The female will then lay approximately 75 eggs. Males will remain with the females anywhere from a few days to three weeks after fertilization occurs.
Mating System: monogamous
Adult mountain pine beetles leave the trees in which they developed during summertime; this is usually sometime during July or August, but could potentially be anytime from mid-June until the beginning of September. At this time, they seek out new trees in which to reproduce. Males fertilize females within these new trees, then females lay about 75 eggs. The eggs hatch into larvae within about 10 to 14 days. Although the parents might remain within the tree for a few days afterward, there has been no parental involvement observed in Dendroctonus ponderosae. Around June or July of the following year, after having developed within the egg gallery throughout winter, the eggs develop into pupae. The pupae then become sexually mature adults sometime around mid-August, and can then leave the Pinus tree to find a mate.
Breeding interval: Mountain pine beetles breed once yearly, or potentially every two years if temperatures are cooler.
Breeding season: Breeding season for mountain pine beetles is in July or August.
Average eggs per season: 75.
Range gestation period: 10 to 14 days.
Range age at sexual or reproductive maturity (female): 1 to 2 years.
Average age at sexual or reproductive maturity (female): 1 years.
Range age at sexual or reproductive maturity (male): 1 to 2 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
No parental involvement has been observed in Dendroctonus ponderosae.
Parental Investment: pre-fertilization (Protecting: Female)
The mountain pine beetle (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 approximately 5 millimetres (1⁄4 in), 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 160,000 km2 (40 million acres) of forest in British Columbia.[1] The outbreak in the Rocky Mountain National Park in Colorado 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 16,000 km2 (4.0 million acres) were affected.[2] The outbreak then declined due to better environmental conditions and the fact that many vulnerable trees had been already destroyed.[2][3]
Mountain pine beetles inhabit ponderosa, whitebark, lodgepole, Scots, jack,[4] limber, Rocky Mountain bristlecone,[5] and Great Basin bristlecone[6] 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.[7]
The outbreak may have been the largest forest insect blight seen in North America since European colonization.[8] 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 gases (such as CO2) from the atmosphere.[9]
Because of its impact on forestry, the transcriptome[10] and the genome[11] of the beetle have been sequenced. It was the second beetle genome to be sequenced.
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.[12] 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.[7]
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.
Beetles develop through four stages: egg, larva, pupa and adult. 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.[13]
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 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:[14]
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,[15][16] 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.[17] 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.[18]
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.[19]
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 and Michael Bennet 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.[20]
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.[21] 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.
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.
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.[22] 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.[23]
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.[24]
The current outbreak of mountain pine beetles is ten times larger than previous outbreaks.[25] Huge swaths of central British Columbia (BC) and parts of Alberta have been hit badly, with over 40 million acres (160,000 km2) of BC's forests affected.[26] 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.[27] 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 900 miles (1,400 km) of trail, 3,200 miles (5,100 km) of road and 21,000 acres (85 km2) of developed recreation sites over 4,500,000 acres (18,000 km2) in Colorado and southeastern Wyoming; other outbreaks encompass the Black Hills of South Dakota and extend as far south as Arizona, 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.
A lodgepole pine tree with a pitch tube
Invaded pine tree forest on the slopes of Chancellor Peak in Yoho National Park, Canada
A pine tree forest north of Breckenridge, CO shows infestation in 2008.
Pine beetle damage in E. C. Manning Provincial Park, British Columbia, Canada, as of August 2010
Mountain pine beetle damage in Rocky Mountain National Park as of January 2012
Mountain pine beetle damage at Hume Lake, California as of April 2016
Previously, cold spells had killed off bark beetles which are now attacking the forests.[28][29] 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.[29][30] 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.[31][32]
Researchers from the Canadian Forest Service have studied the relationship between the carbon cycle and forest fires, logging and tree deaths. They concluded 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, 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'.[25] 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.[33] 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.[34]
Hydrologists from the University of Colorado have investigated the impacts of beetle-infested forests on the water cycle, 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. These thinned canopies also cause faster snowmelt by allowing more sunlight through to the forest floor and lowering the snowpack albedo, as a result of needle litter on the snow surface.[35] Augmented snowpack coupled with dead trees that no longer transpire will likely lead to more available water.
The mountain pine beetle (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 approximately 5 millimetres (1⁄4 in), 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 160,000 km2 (40 million acres) of forest in British Columbia. The outbreak in the Rocky Mountain National Park in Colorado 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 16,000 km2 (4.0 million acres) were affected. The outbreak then declined due to better environmental conditions and the fact that many vulnerable trees had been already destroyed.
Mountain pine beetles 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 seen in North America 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 gases (such as CO2) from the atmosphere.
Because of its impact on forestry, the transcriptome and the genome of the beetle have been sequenced. It was the second beetle genome to be sequenced.
