Some Pines Have Genetic Resistance to Beetles

Scientists seized an unusual opportunity in British Columbia's mountain pine beetle tragedy to investigate whether there is a genetic basis for how well a pine tree resists bark beetles. The beetles put a premature ending to a 20-year-old field trial, that was set up to measure how well different families of lodgepole pines grow, when in 2003 the insects began killing trees in the plantation.

After examining how the various families of trees faired under the beetle attacks, scientists are reporting for the first time that lodgepole pine does have some inheritable traits for resistance to mountain pine beetles.

Two years after beetles first started killing trees at the progeny trial near Prince George BC, 13 percent of the 2500 trees had died, while 63 percent had pitch tubes on their stems where the beetles had burrowed into the tree bark. Within the 165 families of related pines, 46 to 100 percent of trees still survived by 2005. Pines with more than five pitch tubes ranged from 7 to 100 percent of the individuals from a family.

The families belong to three populations, one local and two from elsewhere in BC. Pines with parent trees near Prince George were most likely to be attacked by beetles, with 69 percent of trees having pitch tubes. Somewhat less intensively hit were trees originating from the Chilcotin area, with just over 50 percent of these pines having pitch tubes. The most resistant population is native to the West Kootenay and Shuswap areas of southern BC, with 39 percent of trees attacked.

The data also suggest that rapidly growing trees may have lower defences against infestation from mountain pine beetles. Eleven fast-growing families, though, stood out because their trees seldom had pitch tubes, indicating they resisted attack from beetles. Six of these particularly vigorous families belong to the West Kootenay and Shuswap lodgepole pine population.