WARREN ROOTCOLLAR WEEVIL, HYLOBIUS WARRENI WOOD (COLEOPTERA: CURCULIONIDAE), IN CANADA: ECOLOGY, BEHAVIOR, DAMAGE RELATIONSHIPS, AND MANAGEMENT

Abstract

AbstractWarren rootcollar weevil, Hylobius warreni Wood, is a pest of several conifer species and is distributed widely throughout the boreal forest in Canada. Literature on this weevil is reviewed and interpreted to provide comprehensive coverage of its ecology, behavior, and impacts, and the implications for its management. New information is provided to fill gaps in our knowledge of H. warreni. These include distribution and hosts, immature stages, sex ratios, and daily and seasonal activity patterns of adults. Sex ratios, abundance, longevity, and pedestrian dispersal behavior of adults within the forest and on trees are described from mark, release, and recapture studies conducted over several years using a newly designed interception trap. Daily trap captures are correlated with previous night temperatures and this relationship is a tool for predicting adult captures. Fecundity and oviposition behavior on the host tree are described from laboratory- and field-reared adults.Population levels of H. warreni are compared across a variety of lodgepole pine stands in Alberta. Weevil numbers within forests are described in relation to tree size and age, depth of duff material around tree bases, and stand density. Analysis of weevil feeding scars distributed at the root collar base of mature pine stems were used to describe the likely temporal pattern of population abundance and change during stand development. Information supportive of this pattern is presented from surveys in young and mature stands.A new method of assessing stands of lodgepole pine for suitability of habitat for H. warreni takes into account the cumulative nature of this weevil’s injury and reflects its temporal pattern of success in relation to stand conditions. The effects of a pre-commercial thinning treatment on H. warreni populations and its girdling injury were investigated in a 25-year-old lodgepole pine stand over an 8-year period. Compared with control plots, thinning treatment caused a 5-fold increase in weevil numbers per tree and increased the tree attack incidence by 2-fold, but resulted in an average 6% reduction in partial stem girdling of attacked trees. Information about the effects of various forest management practices on H. warreni abundance and survival is reviewed and areas requiring research are identified.