The mountain pine beetle has been a much talked about insect over the last few years as its numbers have increased substantially as has its range. Here is a description of this important species.
What Is The Mountain Pine Beetle?
Scientific name: Dendroctonus ponderosae
Appearance: Adult mountain pine beetles are black in color and have a hard shell. They are about half a centimetre long (0.2 inches). The larvae are smaller and white.
Pine beetles live in the bark of pine trees. They will not inhabit just any pine tree however. The beetles will usually choose trees that are old, damaged, diseased or under some other form of distress. The pine beetle also prefers larger trees. It is generally agreed that they like trees around eighty years old or older. This is precisely the age of much of the forest areas in North America.
How The Mountain Pine Beetle Spreads
The pine beetle is a burrowing insect. Females bore tunnels or 'galleries' into the bark of trees to lay their eggs. The eggs then hatch and the larvae burrow further into the tree and remain there for the winter. As the larvae move into the pupa stage they remain inside the tree. In summer, adult beetles emerge and set out to find new trees to colonize. When a female chooses a new tree, she releases pheromones which invite both males and females to join her. Many adults can then come and make the new tree home. According to Parks Canada, one beetle can produce enough eggs to colonize 15 additional trees.
How The Mountain Pine Beetle Kills Trees
The way in which mountain pine beetles kill trees is twofold. While the larvae are inhabiting the tree over the winter they feed on it, creating more and more tunnels in the bark. This tunnelling damages the layer of the tree called the phloem layer. This part of the tree is responsible for distributing nutrients throughout the tree. In essence, the work of the beetles starves the tree as well as consumes it. The beetles also carry with them blue stain fungi. These fungi attack the xylem (or water transportation system) of a tree. Now the tree is not only starved, but also deprived of fluids as well. Trees colonized by mountain pine beetles can be killed by an infestation in the span of one year. It is easy to recognize a stand of infested trees by their distinctive red color.
The Benefits Of Mountain Pine Beetles
Though in recent years the pine beetle has developed some notoriety for killing forests, in smaller numbers, these beetles can be beneficial to an ecosystem. They help contribute to forest succession. In other words, they kill off older trees which then provide housing for animals as they decay. Eventually they break down and nourish the newer trees in the area. As these older trees are diminished more sunlight is able to penetrate to the forest floor, encouraging even more new growth. The beetles are also consumed as food by other species in the forest. The woodpecker, for example, has learned to capitalize on this species.
Why There Is Now A Problem
There are currently several factors affecting the abnormal proliferation of the mountain pine beetle. One such factor is the prevention of forest fires by humans. Natural fires tend to occur in the same types of areas that these beetles prefer to inhabit, thus the fires keep the population in check. When we put out the fire we are, in essence, saving the lives of many pine beetles. Global warming is another contributing factor since the beetles are culled by extreme temperatures. While species such as the ice beetle are loosing ground due to global warming, the pine beetle is gaining ground. They are able to move further and further north as temperatures are more and more moderate, giving the beetles an ever increasing range. If you couple these factors with the fact that many of North America's forests are also of the preferred age, then this area has the potential for enormous population growth for these creatures.
Photo Credit
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