The mountain pine beetle (MPB) or Dedroctonus ponderosae as known in the scientific name is a species that belong to the bark beetle common in the western North America forests starting from Mexico to the British Columbia forests. The beetle is black with a hard shell and they inhabit pines, hence the name Mountain pine beetles. The pine species that are habitat to these beetles are mainly Ponderosa pine, Scots pine, Lodgepole pine, and the Limber pine. The less attacked species of pine are the bristlecone pine and pinyon pine.
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The trees attack begin with the injured trees, trees with in poor site, infected trees in the roots or stem, fire damaged trees, overcrowded trees and the very old trees during the first stage of the attack of these beetles. However with the increase in their population the beetles attack all the trees regardless of their conditions. The infestation of the beetle has threatened the presence and the existence of forests in the British Columbia, Mexico and Canada. The outbreaks of the mountain beetles in the past have destroyed much of the forests and the recent outbreak which is the largest is posing great risk to forest destruction. These piece of work looks into the infestation of the mountain beetle, its effects, prevention and control measures towards the reduction of the beetle’s attack on the American forests.
Tree infestation of the Mountain Pine beetle
The beetles are very dangerous and destroy and kill the tree within a short time. The beetles bore through the bark of the tree and enter the in the phloem and feed on its sap and lay their eggs. The initial tree attack is done by a pioneer female beetle. After its first attack, it produces pheromones, a type of hormone from their bodies that attract more beetles for mass attack of the tree. (McMullen, 1999)
The trees when attacked increase the production of resin that kill the beetle but the beetle also counteract this resin by the blue stain fungi that they carry along that block the tree’s resin production. With two weeks time, the attacks on the phloem of the tree becomes so intense that the phloem tissues are damaged such that the transportation of food to the branches is impaired which result to the death of the tree. The tree changes the color of its needle like leaves (a characteristic of pine tree) to reddish which is a clear indication of starvation of the tree by lack of water and food that result from the damage of the phloem and the xylem tissues that transport food from the root to the leaves. The trees that are vulnerable are the old trees and the already disease infected trees that die faster than a healthy tree. The beetle’s infestation usually occurs after a long hot summer period. At this time their number is uncontrollable and the damage is widespread with the destruction of large areas of mountain rock pine forests.
Life History of the Mountain pine beetle
The mountain pine beetle has a one year life cycle in Colorado USA. The adults leave the dead yellow reddish trees they have attacked during summer to green trees where they begin new attacks by tunneling under the tree bark. The female adults prefer large diameter trees where they are able to lay their eggs and feed. During massive attacks however, they may also attack the small trees. The beetles carry out massive attacks after which every beetle pairs with a mate forming a long vertical tunnel under the bark where each pair of mate lays about 75 eggs where they hatch into larvae.
The larvae spends the cold winters under the bark of the tree by metabolizing glycerol, a type of alcohol that enable them to survive the winter through its action that freezes the air for insulation purposes. In June and July the larvae change to pupa and later in September, they develop into adults. In lodgepole pine the adults exit the tree earlier in late July and in the ponderosa pine, they may leave in mid august. (Douglas, 2001)
The beetle’s unique lifestyle especially their ability to transmit bluestain fungi, The spores of the fungi poison the body of the adult beetle and during attack, they are introduced into their body where they enter the tree and the fungi grow within the tree assisting the beetle in destruction and killing of the tree.
Signs and symptoms of trees attacked by the MPB
Trees that have been attacked by the Mountain pine beetle shows the following signs:
- The trees develop masses of resin that are pop con shaped. These masses of resin are or pitch tubes forms where the tunneling of the beetle began and they can be either pink or white in color.
- At the base of the tree and bark crevices, dust that is produced as a result of boring through the tree by the beetle can be observed.
- When a tree is attacked by the beetle, there are several wood peckers feeding on the tree take advantage of the exposure of the inner wood by the beetles. Flakes of tree can also be seen at the base of the tree which has been produced by the wood peckers.
- The presence of the beetle’s eggs, larvae, pupae and the adults in the barks of the tree can be seen at the first stages of attack. Identification of their presence at this stage can be controlled through use of protective chemicals.
- Blue stained sapwood is also seen around the tree, which is as a result of the interaction of the resin and the blue stain that the beetles posses for their protection.
- The foliage of the tree changes to reddish which comes at the later stage of attack by the mountain pine beetle, usually the tenth month after attack. This is the critical point and the tree is completely damaged.
Once a tree is infested by the Mountain pine beetle, there is very little that can be done to save the tree. The beetles destroy the tree in mass attacks and from the tree they have attacked, holes of free exit can be seen and the tree cannot be treated. Early in summer, the Ips beetle that are similar to the MPB beetles also attack although they are not very dangerous. It is also difficult to predict the direction of spread and infestation of the mountain pine beetles which makes it difficult to protect trees. Attacked trees however are usually next to the previously killed trees.
Control of the MPB
Since it is impossible to treat trees attacked by the Mountain pine beetles, it is important to protect the trees from these attacks through the control of the beetle. The beetles can be controlled naturally by the use of natural biological methods such as the wood peckers and other insects present in the forests which feed on the adult beetle, lava and their eggs. During outbreaks, the natural methods are overcome by the mass infestation and they fail to control the tree attack. (McMullen, 1999)
Another natural control of the mountain pine beetle is the extreme cold temperatures during winter. The fall of snow before the larvae metabolizes glycerol can be effective as it leads to their death before they change to adults. In late spring, before the moulting of the insect in to pupa is a vulnerable stage in life and cold can destroy their development hence enhance their control. Temperatures lower than zero Fahrenheit lasting for at least five days can help in destruction of a large number of larvae.
Treatment of trees
Trees infested by the mountain pine beetle can be treated at very early stages. This can be done by destroying the developing beetles before they change into harmful adults in summer. The larvae can be killed by removing the bark of the tree to expose the larvae to unfavorable conditions. The larvae become dehydrated as it relies on the tree for moisture and also starves to death. Peeling of the bark can be done manually or mechanically and it is labor intensive.
The logs can be burned on snow to prevent forest fires. They can also be buried in the soil at least 8 inches. The use of the wood can continue during emergency of the beetles which help in their control.
There have not been a known pesticide so far to control the MPB but the use of insecticides is also effective in destruction and control of the mountain pine beetles, the solar treatment whereby the temperatures in the forests are increased to about 110 degrees. Although it is labor intensive it is also effective in the control of the MPB.
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The mountain pine beetle can be prevented from infestation through proper forest management. The MPBs infest in forests that are old or densely populated forests. Management should involve creating diversity in the structure and the age of the forest to prevent the trees from MPB infestation. Healthy forests, with young and sparsely populated trees are less vulnerable to attack by the beetles.
Carbanyl, Permethrin and Bifethrin are chemicals that are registered for the attack prevention of the trees from the MPB. They are applied on healthy green trees to protect them from attack. This process can be done annually. However the chemical may not be more effective in case of a massive outbreak due to various reason that result use of these chemicals. These include:
Problem in identification of healthy trees during dry condition when trees do not produce pitch tubes if they are infested hence it is not easier to tell which trees are healthy and which are infested. The timing is also very important; spraying done after June may not be effective as the trees have already been attacked.
The spraying may not cover the tree as required thus produce undesired results. Patches left uncovered with the spray may give room to attack by the beetles.
The outbreak of the mountain pine beetle is vast as compared to the previous years. The outbreak is 10 times more and there is fear in Alberta over the outbreak, however there is hope for control as the extreme cold that began in the start of 2008. This may help a great deal. (Douglas, 2001)
Effects of the MPB infestation on the Carbon Cycle
From research carried out in the Canadian forests, researchers found out that from the carbon dioxide released in the atmosphere from forest fires logging and tree deaths is far much lower as compared to the ones released by the mountain pine beetles. It is estimated that by the year 2020, 270 mega tonnes of Carbon dioxide will be released to the atmosphere by the beetle’s outbreak. This poses great dangers to the global warming that the world is trying to reduce. Canada has been targeting to reduce its carbon level in the atmosphere but the recent research has proved the impossibility of reaching this target.
Areas infested by the Mountain pine beetle
The outbreak of the beetle in the British Columbia forests has been a great issue facing forests for many years. The mountain beetle has destroyed over 300,000 acres of forests in British Columbia since 1997. The lodgepole pine has been more vulnerable. The forests are facing a double danger due to the logging companies that are logging in large scale using the epidemic of the beetles as a cover up. In the previous outbreak in the British Columbia, the mountain beetle has killed over 80 million trees in over 450000 hectares that have made them the second largest disaster in the forest after fire.
The forest ministry has aggressively logged in the forest as a mean of stopping the mountain beetles which cannot work out. However this is a short term benefit tot the government through the utilization of the destroyed trees. These are not the solutions to the protection of forests but rather a way to finish them. The massive clearance can lead to forests remaining with old stands of trees that are more vulnerable to attack by the beetles. (McMullen, 1999)
However the process of harvesting the affected trees can be effective in the reduction of the beetles attack if and only if it is combined with other prevention measures such as the early detection of the beetle’s infestation and spraying.
Advantages of beetles’ infestation in the forests
The mountain beetles help in improving the productivity of the forest through a sustainable ecosystem based management which allow the removal of the old trees and thinning to avoid overcrowding as a way to reduce vulnerability and on the other hand improve the productivity of the forest.
The mountain pine beetles also help to log down trees that form habitat for other insects in the forest and they also provide food for birds such as the wood peckers. This is an important aspect in the preservation of the ecological diversity in the forests in America. (Michael, 2005)
The effective solution to the mountain pine beetle can only be achieved through establishment of a sound ecosystem approach. This approach will take into account the entire forest ecosystem instead of focusing on the beetles. By considering other factors in the forest, the balance in ecosystem can be achieved at the same time reducing the rate of infestation of the mountain pine beetle.
The mountain beetles infestation can be straining to the economy as their controls require use of resources. The transportation of the affected logs from the forest is very expensive. (Mike, 2000) The prevention and control measures such as spraying, bark peeling, and the burning of the logs affected by the mountain beetle are labor intensive. However the natural methods that are more convenient and economical cannot be entrusted in coping with massive outbreaks and other methods have to be applied.
The infestation of the mountain beetles have attracted a lot of researchers interested in studying about the ecosystem. The researchers are also focused in coming up with a reliable long term solution to the beetle’s infestation that is threatening the forests in the western North America. Fears of the beetles spreading to other parts of the world have made several countries to invest in research especially universities for example the university of Colorado which is carrying out extensive research on the beetle’s infestation.
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Douglas, L. et al, (2001). Mountain Pine Beetles in the American Forests, New York: Macmillan Publishers.
Gene, D. and Kevin, C. (2003). Using Pheromones to Protect Heat- Injured Pine from Beetles, Colorado: University of Colorado.
Joanne, W. (2002). Mountain Pine Beetle, Columbia: Government Publication.
Michael, A. (2005). Enhancing Forest Inventories with Mountain Pine Beetle Infestation Information, Colorado: Pacific Forestry Center.
Mike, P. (2000). Regional Economic Implication of the Mountain Pine Beetle, New York: McGraw-Hill.
McMullen, L. et al, Suppression of Mountain Pine Beetle, Columbia: Columbia University, 1999.