Blue-stain Fungi Thrive in Jack Pine

As British Columbia's massive mountain pine beetle infestation spreads eastwards, the question still remains as to whether the beetles can successfully invade Canada's boreal jack pine forests. Part of the answer to that question lies in whether the blue-stain fungi associated with the beetles in lodgepole pine can also survive in the closely-related jack pine.

Research now shows that two species of blue-stain fungi, Grosmannia clavigera and Ophiostoma montium are even more virulent in mature jack pine than in lodgepole pine. The larger these fungi grow through a tree stem's phloem and sapwood, the more likely they can kill a tree.

Within six weeks of small amounts of the fungi being introduced to trees in Alberta, the fungi growing in lodgepole pines averaged only two-thirds the length of that in jack pines. Tree that are hybrids of the two species had fungal infections of intermediate lengths. Lodgepole pine appears to have a natural resistance to these fungi that jack pine lacks.

The mistletoe infection weakening some trees had no bearing on how well the fungi did. But several other factors did influence fungal growth. For instance, certain genetic strains of G. clavigera were much more aggressive than others.

Whether the fungi's success means that the beetles will thrive in the jack pine forests is another matter. Some amount of blue-stain fungi seems essential to the beetle's survival. These results indicate that a lack of fungi will not constrain the beetles' expansion into jack pine forests.

But it remains unanswered whether too much fungal growth is detrimental to mountain pine beetles. Nevertheless, these research results do show that the tripartite relationship between bark beetles, fungi and jack pine trees will have a different balance than what exists in lodgepole pines.