Screening of Sitka spruce genotypes for resistance to the white pine weevil using artificial infestations

Sitka spruce (Picea sitchensis (Bong.) Carr), white spruce (P. glauca (Moench) Voss) and Engelmann spruce (P. engelmanni (Parry)) plantations in British Columbia (B.C.), Canada, have come under serious attack from the white pine weevil, Pissodes strobi (Peck) (Coleoptera: Curculionidae). This pest attacks and destroys the terminal leader of the tree, causing serious growth losses and stem deformities. Since 1993, we have conducted a series of screening trials to search for spruce with resistance to the white pine weevil. Spruce tree selections from across the range of the species have been planted in several replicated trials. At 12 of these trial sites, in order to accelerate the screening process, local insect populations were augmented by adding reared weevils to the site. Results from our two oldest trials, at Jordan River and Cowichan Lake (planted in 1994), both on Vancouver Island, B.C., indicate that screening for weevil resistance can be effectively accomplished by using the weevil population augmentation method. Consistent selections could be obtained in trials with as few as 10 replicates per family. If weevil attack rates of 50% cumulative attack are obtained, then consistent selections may be obtained in as little as 4 years, which is a fairly quick turn-around time for studying resistance in trees.