Pine beetles use different strategies to attack trees

A new study from the University of Alberta describes the different strategies used by female pine beetles to colonize trees, and their success comes along with major consequences for pine forests.

Over the last three decades, an outbreak of mountain pine beetles has affected more than 18 million hectares of forest in Western Canada. 

Led by graduate student Kelsey Jones, a team of biologists investigated the ability of mountain pine beetles to become established based on the distance they travel to new host trees.

The study revealed that the female beetles were successful whether they traveled to pine trees just a few meters or tens of kilometers away.

Some beetles stay close to home, traveling no more than a couple of meters, while others target trees more than 30 kilometers away. The experts found that the beetles have developed different invasive strategies based on the distance of their flights.

“Both long and short-distance flight strategies are beneficial to mountain pine beetle host colonization in different ways,” said Jones. “As short- and long-distance flyers successfully colonize host trees for reproduction, both strategies will remain in the population, maintaining genetic variability.”

The study showed that female pine beetles who travel long distances usually lose weight, but are able to produce the most pheromone. This strengthens their ability to attract other distant beetles and launch a massive attack.

Meanwhile, beetles who stick close to home produce the smallest amounts of pheromone. However, these beetles do not lose much weight and save their energy to focus on colonization.

According to the researchers, understanding the behavior of pine beetles is critical for developing management strategies to prevent further damage to Alberta’s boreal forest.

“It is hard to predict the continued invasion by the mountain pine beetle using information from this study alone,” said Jones. “However, our work does indicate that beetles which fly for long distances can still call in many fellow beetles to mass attack trees. This indicates that, as beetles move further eastward and forest stands become thinner, they will likely still have the capacity to colonize hosts.”

The study is published in the Journal of Experimental Biology.

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By Chrissy Sexton, Earth.com Staff Writer