Constitutive defenses and damage in Sitka spruce progeny obtained from crosses between white pine weevil resistant and susceptible parents

The white pine weevil, Pissodes strobi Peck (Coleoptera: Curculionidae), is a serious forest pest in young pine and spruce plantations in much of Canada and the northern US (Mitchell et al., 1990; Alfaro et al., 1995). Adults emerge in early spring to begin feeding and egg laying in the secondary phloem of the1-year-old terminal leader of young trees (Silver, 1968). Upon hatching, larvae mine downward consuming the secondary phloem, girdling and killing the leader (Silver, 1968). This pest causes serious economic impact since leader damage cause large reductions in height growth and severe stem deformations, such as crooks and forks (Alfaro, 1989). In Western North America, this insect causes damage to Sitka spruce (Picea sitchensis (Bong.) Carr) (Alfaro et al., 2000), white spruce (Picea glauca (Moench) Voss) (He and Alfaro, 2000), Engelmann spruce (Picea engelmannii Parry) (Mitchell et al., 1990) and interior spruce (Picea glauca × Picea engelmanni) (Taylor et al., 1996). Among these species, Sitka spruce is particularly vulnerable to weevil damage. During the past decades, thousands of hectares of young Sitka spruce were planted annually in Canada and the US, but damage by the white pine weevil has forced managers to severely reduce the planting of this species. For example, in British Columbia (BC), Sitka spruce plantings have been reduced from a historic level of 10 million to fewer than 1 million trees annually (King and Alfaro, 2009). Constitutive defenses and damage in Sitka spruce progeny obtained from crosses between white pine weevil resistant and susceptible parents