Fungal infections in trees can hurt — or help — in the battle against mountain pine beetles

Researchers at the University of Alberta have investigated how fungal pathogens affect the ability of trees to defend against attacks by mountain pine beetles.

"Different fungal pathogens can affect the chemistry of the tree differently," Rashaduz Zaman, lead author of a study published in the journal Microbial Ecology, said in an interview last week.

Zaman, who is pursuing a PhD in forest biology and management, worked with fellow researchers to test the effect of several fungal pathogens on the self-defence ability of lodgepole pine, one of the most abundant coniferous trees in North America.

Lodgepoles make up about 35 per cent of forested land in Alberta and British Columbia.

The aim of the research was to contribute to the development of forest management strategies that take into account the chemical profiles of trees, Zaman said. 

The researchers looked at two of the most common fungal pathogens that infect mature lodgepole pine trees in Western Canada — Atropellis canker and western gall rust.

They also looked into how symbiotic fungal pathogens associated with the mountain pine beetle impacted the trees' ability to produce compounds toxic to the beetle. 

Fungal pathogens play an important role in the mountain pine beetle establishing itself under the tree's bark, said Jakub Olesinski, a forest health specialist with Parks Canada who wasn't involved with the study.

Beetles build tunnels under the tree's bark, called galleries. When they build egg galleries, "the sapwood of the tree is inoculated with spores of the blue stain fungus," Olesinski said. 

He said the fungus prevents the tree from repelling and killing the attacking beetles.

The U of A researchers found that symbiotic pathogens associated with the pine beetle, and western gall rust, weakened the trees' defences by reducing the production of terpenes — compounds that help the tree protect itself against infection and infestation.