FEEDING AND OVIPOSITION PREFERENCES OF WHITE-PINE WEEVIL (COLEOPTERA,CURCULIONIDAE) ON RESISTANT AND SUSCEPTIBLE SITKA SPRUCE CLONES IN LABORATORY BIOASSAYS

White pine weevils, Pissodes strobi (Peck), caged on live clones (graf ts) of resistant and susceptible Sitka spruce trees, Picea sitchensis (Bong) Carr., and petri dish experiments using cut branches from the s ame clones demonstrated that P. strobi feeding and oviposition was neg atively correlated with the density of resin canals in the bark of the host tree. Weevils in cages containing resistant trees fed and ovipos ited preferentially in the internode below the leader where resin cana l density was lower (i.e., only the leader and not the entire tree was resistant). However, if given a choice, weevils departed from resista nt trees and aggregated on susceptible trees. These experiments indica te that resistance is based on blockage by the tree of the normal pref erence of P. strobi for feeding and oviposition on the leader This blo ckage is probably caused by repellency caused by the high resin concen tration in the leader which, under natural conditions, forces the weev ils to depart from resistant trees. The interaction of the weevil with other resistance mechanisms is discussed.