MacLean D FEMC2007

Spruce budworm and management planning

David MacLean, Faculty of Forestry and Environmental Management, University of New Brunswick, P.O. Box 44555, Fredericton, NB, E3B 6C2, Canada, macleand@unb.ca

Mountain pine beetle is currently Canada’s most damaging insect, but from 1975-2000, when 709 million hectares of Canada’s forest sustained moderate-severe (>30%) defoliation or beetle-killed trees, almost two-thirds was caused by spruce budworm (Choristoneura fumiferana). During major outbreaks in the 1970s-1980s, budworm defoliation caused 80-100 million cubic meters of timber loss per year. Budworm selectively kills and reduces growth of spruce-fir, reduces stand yield, alters harvest schedules, and generally nullifies management plans.
Management actions to deal with spruce budworm outbreaks include 1) spraying insecticides to prevent defoliation and keep trees alive and/or maintain growth increment; 2) salvage harvesting of dead trees before they are no longer usable due to rot; 3) planting nonsusceptible species such as jack pine or hardwoods, or low-susceptibility species such as black spruce; 4) forest restructuring using precommercial thinning or harvest scheduling to reduce occurrence of fir and spruce at the stand or landscape level; or 5) doing nothing and incurring the resulting growth reduction and mortality. ‘Traditional’ chemical insecticides (e.g., fenitrothion, aminocarb) formerly used against spruce budworm have been replaced by the biological insecticide Bacillus thuringiensis (B.t.) or the insect growth regulator tebufenozide (Mimic®).

The Spruce Budworm Decision Support System (SBW DSS) was developed to assist in spatial decision making related to budworm management. It uses: 1) forest inventory and budworm monitoring data to describe the landbase and determine outbreak scenarios; 2) stand yield and harvest schedule data from management plans for the area; 3) a stand growth model (STAMAN) and timber supply (forest estate) model (Woodstock) to determine stand- and forest-level effects of defoliation and protection; 4) the ARC/INFO GIS and custom programs for calculations and spatial data manipulation; and 5) ArcView for map generation and a graphical user interface. Because of the direct use of existing management plan yield data and harvest schedules, the DSS is implemented separately for each forest management unit.

The SBW DSS calculates the timber supply consequences of alternative management actions and thereby facilitates incorporation of effects of insect damage into forest management planning. It permits evaluation of costs, benefits, and consequences of management, assists in optimizing insecticide use (if desired), and improves visualization of consequences of pest outbreaks and management strategies on forest performance indicators. The Protection Planning System (PROPS) component quantifies the marginal timber supply benefits of protection and provides the ability to determine the effects of different budworm protection strategies on forest development and timber supply. The SBW DSS has been implemented for all of New Brunswick, and test areas in AB, SK, ON, and QC. DSS projections for NB indicate that potential timber losses on the 5 million ha of spruce-fir are 82 million cubic meters for a normal outbreak scenario and 203 million cubic meters for a severe outbreak scenario, where the difference was an extra 2 years of defoliation. Recent developments using the SBW DSS for economic analyses and modifications to use linear optimization of harvest scheduling, salvage and insecticide application to minimize volume reduction will be described. On a 200,000 ha landbase in NB, simulations results suggest that planning combining optimized salvage and harvest re-scheduling could reduce future harvest reductions by 12%.