Canadian Forest Service Publications
Mechanisms of resistance in conifers against shoot infesting insects. The case of the white pine weevil Pissodes strobi (Peck) (Coleoptera: Curculionidae) 2002. Alfaro, R.I.; Borden, J.H.; King, J.N.; Tomlin, E.S.; McIntosh, R.L.; Bohlmann, J. Pages 105-130 in M.R. Wagner, K.M. Clancy, F. Lieutier, and T.D. Paine, editors. Mechanisms and Deployment of Resistance in Trees to Insects. Kluwer Academic Publishers, Netherlands. 332 p.
Issued by: Pacific Forestry Centre
Catalog ID: 20578
A variety of insects feed on conifer shoots. These include: defoliators, bark wood and cone borers, girdlers, gall makers and sucking insects, primarily in the orders Lepidoptera, Coleoptera, Hemiptera, Homoptera and Diptera. However, these insects usually do not have an exclusive feeding niche. Some also feed on buds, foliage, stem and cones. For example, larvae of the pine shoot moth, Rhyacionia buoliana Schiff., feed on shoots and cones, in addition to mining inside the newly expanding shoots. Adults of the lodgepole terminal weevil, Pissodes terminalis Hopping, and the white pine weevil, Pissodes strobi Peck, feed on the one-year old or older bark of stem and branches, but the larvae feed exclusively on inner bark of the uppermost tree internodes. As young larvae, spruce budworms, Choristoneura spp., are bud miners, but move to feed on cones and expanding new shoots and foliage as they mature. An important group of shoot infesting insects includes the weevils (Coleoptera: Curculionidae), with the most important genera being Pissodes, Cylindrocopturus and Magdalis. Among these, the white pine weevil is the most important pest of spruce (Picea spp.) and pines (Pinus spp.), in North America (Alfaro 1994; Lavallée and Benoit 1989), and is used in this review as an example to describe defences in conifers to shoot insects. In early spring (late March, April), adults of this weevil emerge from overwintering in the duff, and after mating, females oviposit in the upper section of the previous year's leader. The larvae mine downwards, consuming the phloem, girdling and killing the leader. Pupation occurs in chambers excavated in the xylem. Adults emerge from the leaders from late July to September, and when temperatures drop and photoperiod shortens, they go into hibernation in the duff (Silver 1968).