Natural Resources Canada, Canadian Forest Service
SERG Project #2006/09
Year of Project: 2006
Report Received: 2007
Since the mid-1980s, the mountain pine beetle (MPB) has spread at least two degrees latitude northward in Alberta. Beetle populations have persisted in the Wilmore Wilderness area for the past 6-7 years, and dramatically increased over the winters of 2004/05 and 2005/06. In the summer of 2006, the MPB spread at least 250 km into northwestern Alberta from populations in northeastern BC. Thus, the MPB has now successfully invaded the boreal forest of Alberta, infesting both lodgepole pine and lodgepole-jack pine hybrids. There is no evidence yet that jack pine has been infested by MPB, but resident MPB populations are within 100 km of pure jack pine stands. If beetle populations become established in jack pine, this will establish a potential conduit for MPB to move further eastward in the boreal as well as southward to the pine species in the southeastern USA. Thus, the continued eastward dispersal of MPB is of great concern to Alberta and jurisdictions further east.
The MPB attacks and kills many native and introduced pine species within its range. Jack pine, which ranges across the boreal region from Alberta to the east coast, is taxonomically and chemically similar to lodgepole pine. The MPB can successfully reproduce in cut bolts of jack pine, but this success cannot be extrapolated to natural stands of healthy, living trees. The question of whether MPB can successfully invade jack pine is critical to address as there are direct implications for management planning in boreal forests. While the question cannot be answered directly without risking the introduction of MPB into jack pine stands, it can be addressed experimentally. In a controlled rearing experiment, we introduced pairs of MPB into cut bolts of lodgepole, jack and hybrid pines in the lab to assess relative success and performance of MPB in each host.
Langor (1989) demonstrated that MPB utilize more of the bole and have higher fecundity and survival in limber pine than in lodgepole pine, ostensibly because limber pine has thicker phloem. The relationship between jack pine diameter, phloem thickness and the capacity of MPB to attack, breed, and survive is critical in applying risk ratings to jack pine stands. Thus, we assessed the relationship between tree diameter and phloem thickness for jack pine and hybrids across Alberta and Saskatchewan.
The possible spread of MPB to jack pine has serious economic, social, and environmental implications for Canada. Climate-based models predict that MPB can spread to jack pine. At this time, the biological basis for such models is weak because there is little empirical evidence suggesting that jack pine is a suitable host for the beetle. The work proposed herein will fill this gap by providing the basis to adapt such models to reflect biological realities. The outcomes of this research will provide land managers and the forest industry with a realistic ‘heads-up’ regarding the risk of boreal pine forests to MPB, and will enable appropriate proactive planning.