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Mountain pine beetle

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Mountain pine beetle
Adult mountain pine beetle
Dendroctonus ponderosae
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Insecta
Order:
Coleoptera
Family:
Scolytidae
Subfamily:
Scolytinae
Genus:
Dendroctonus
Species:
D. ponderosae
Binomial name
Dendroctonus ponderosae
Hopkins, 1902

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 shell and measures about 5 millimetres, about the size of a grain of rice.

Mountain pine beetles inhabit pines, particularly the Ponderosa Pine, Lodgepole 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, 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.

There are some defenses. Owners nail to a tree an “aggregator 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.[1]

Life cycle

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.[2] The lifespan of a single pine beetle is about one year.[3]

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.[4] 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). [5] It may be the largest forest insect blight ever seen in North America.[6] 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. [7] 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.

See also

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.[4]

See also

References

Wikispecies has information related to Mountain pine beetle.
  1. ^ Robbins, Jim (2008-11-17). "Bark Beetles Kill Millions of Acres of Trees in West". New York Times. {{cite news}}: Italic or bold markup not allowed in: |publisher= (help)
  2. ^ Mountain Pine Beetle, Alberta Sustainable Resource Development
  3. ^ Mountain Pine Beetle - Ministry of Forests and Range - Province of British Columbia
  4. ^ a b "Beetles may doom Canada's carbon reduction target: study". 2008-04-23. Retrieved 2008-04-28.
  5. ^ "Bark Beetles Kill Millions of Acres of Trees in West". 2008-11-17. Retrieved 2009-02-09.
  6. ^ "In the Rockies, Pines Die and Bears Feel It". 2007-01-30. Retrieved 2009-02-09.
  7. ^ Platt, Michael (2008-03-13). "Millions of tiny, pine beetle corpses!". Calgary Sun. {{cite news}}: Italic or bold markup not allowed in: |publisher= (help)
Wikimedia Commons has media related to Dendroctonus ponderosae.
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