MULTICOMPONENT INDEX FOR EVALUATING RESISTANCE BY SITKA SPRUCE TO THEWHITE-PINE WEEVIL (COLEOPTERA, CURCULIONIDAE)

A prototype multicomponent resistance index was constructed for use in the selection of parent trees for a Sitka spruce, Picea sitchensis Bo ng (Carr.), breeding program and screening of progeny for resistance a gainst the white pine weevil, Pissodes strobi (Peck). Data describing density of outer resin ducts, bark thickness, amount of volatile folia r amount of cortical diterpene resin acids, feeding and oviposition de terrency, and were collected from a clonal trial on Vancouver Island. These data were resistance index based on their hypothesized importanc e in weevil host selection. Clones differed in their complements of re sistance traits, indicating that resistance is probably polygenic. The re was a significant negative relationship between the resistance inde x and number of weevil attacks for the clones examined, suggesting tha t the resistance index could predict the resistance status of the tree s. This relationship was improved if feeding deterrency and repellency were removed from the index. Our results suggest that a multicomponen t resistance index is a promising tool for screening for resistance to P. strobi.