Pine beetles successful no matter how far they roam—with devastating effects

New U of A research suggests beetle infestation in Canada will continue to spread eastward despite thinner tree stands.


A mountain pine beetle in a "flight mill" used to test how fast and far it can fly. A new study shows female beetles are adept at finding new host trees whether they travel just a few metres or more than 30 kilometres—which suggests the pests are likely to keep spreading eastward across Canada. (Photo: Journal of Experimental Biology)

Whether they travel only a few metres or tens of kilometres to a new host tree, female pine beetles use different strategies to find success-with major negative consequences for pine trees, according to new research by University of Alberta biologists.

Graduate student Kelsey Jones led a study examining the relationship between host colonization success by female mountain pine beetles and the distance travelled to find their new homes.

"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 farther eastward and forest stands become thinner, they will likely still have the capacity to colonize hosts."

Since the early 1990s, an outbreak of mountain pine beetles has affected more than 18 million hectares of forest in the western provinces.

Some beetles fly distances of more than 30 kilometres while others stay close to home, travelling no more than two metres away to find a new host tree.

"Both long- and short-distance flight strategies are beneficial to mountain pine beetle host colonization in different ways," explained Jones, who completed her master's under the supervision of biologist Maya Evenden.

"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 that travelled long distances tended to lose weight, but were able to produce the most pheromone, signalling their arrival to other beetles and increasing their chances of attracting beetles from distant populations to facilitate mass attack of tree hosts.

On the other hand, beetles that stuck close to home lost the least amount of weight but also produced the smallest amount of pheromone, instead focusing their energy on host colonization.

Jones noted the work will be used to inform models of how mountain pine beetles spread throughout the boreal forest, assisting efforts to monitor and control beetle populations and prevent further damage.

The study, "Mechanisms and Consequences of Flight Polyphenisms in an Outbreaking Bark Beetle Species," was published in the Journal of Experimental Biology.