RELATIONSHIP BETWEEN LEADER MORPHOLOGY AND RESISTANCE OR SUSCEPTIBILITY OF SITKA SPRUCE TO THE WHITE-PINE WEEVIL

Sitka spruce, Picea sitchensis (Bong.) Carr., from 27 provenances and five sites in British Columbia, were examined for traits of leader mor phology that might be involved in resistance to the white pine weevil, Pissodes strobi (Peck). Trees from the Usk Ferry provenance at Head B ay and the Kitwanga provenance at Nass River both had low incidence of weevilling, and had needles pressed more closely against the stems by up to 20-degrees than trees from other provenances. At Fair Harbour, trees from the two most resistant provenances, Haney and Cedarvale, ha d inner resin ducts that were approximately twice the diameter of thos e in trees from the most susceptible provenances. Resistant trees from these two provenances also had significantly more outer resin ducts t han those from any other provenance planted at any of the five sites. Values ranged from 28 outer ducts per centimetre for Haney trees, to < 1 per centimetre for very susceptible trees from the Masset Sound prov enance in the Queen Charlotte Islands, where the absence of weevils co uld have eliminated any selection for trees with a high density of res in ducts. We hypothesize that trees from the Haney and Cedarvale prove nances may have large numbers of outer resin ducts as an important res istance mechanism, which could be used as a selection criterion for re sistance. Resistant trees from other provenances such as Big Qualicum, Kitwanga, and Green Timbers, which have fewer outer resin ducts than those from Haney and Cedarvale, must rely heavily on mechanisms other than those associated with the resin system morphology.