Here’s your weekly Science Matters column by David Suzuki with Faisal Moola.

Little bug, big problem

Human beings are obsessed with size. We want bigger cars and bigger
houses, and, of course, men want bigger you-know-whats. But big isn’t
everything. A tiny insect about the size of a grain of rice, the
mountain pine beetle, has devastated British Columbia’s interior pine
forests, threatening enormous social, economic, and ecological
upheaval. The infestation, which is expected to kill close to 80 per
cent of B.C.’s mature pine forests, was caused in large part by global
warming and is now seen as a contributor to the problem that caused its
outbreak in the first place.

How can something so seemingly insignificant cause so much
damage? The mountain pine beetle (Dendroctonus ponderosae) is a
naturally occurring insect that starts its attack when a female uses
its senses to find a pine tree (usually lodgepole) that is at least 80
years old. On finding a mature tree, she bores into it while releasing
a pheromone that attracts male beetles. When the sex-crazed males
arrive, they in turn secrete pheromones that attract more females. The
tree mounts a response by secreting a toxic resin that beats back a few
beetles. But the beetles have another trick up their sleeves – or in
their mouths. They carry spores of a blue-stained fungus, which are
released as they bore into the tree. The fungus puts a stop to the
spread of resin and allows the beetles to keep tunnelling.

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