Temptations of weevil: feeding and ovipositional preferences of Hylobius warreni on bark in laboratory bioassays

Warren root collar weevil Hylobius warreni Wood (Coleoptera: Curculionidae) is a native, long-lived, flightless insect distributed throughout coniferous forests across Canada. Adult weevils feed on all life stages of a variety of coniferous hosts. While adult feeding is not detrimental, larvae may girdle and kill young trees. Hence, the insect poses considerable challenges to reforestation. The relative feeding preferences of these insects have never been quantified, however. Moreover, it is not known if host bark influences oviposition behaviour. We examined feeding preferences of adult weevils on small branches of three conifers (lodgepole pine Pinus contorta var. latifolia, interior hybrid spruce Picea glauca x engelmannii, and Douglas-fir Pseudotsuga menziesii) and one deciduous tree (trembling aspen Populus tremuloides) using choice and no-choice laboratory bioassays. We measured the surface area of bark consumed, the rate of consumption, the number of days of feeding, and, in the no-choice assay, the numbers of fecal pellets and eggs oviposited. Bark consumption was greatest on pine and Douglas-fir, followed by spruce. Little feeding occurred on aspen in the no-choice bioassay, and the presence of aspen branches did not inhibit feeding on any of the other species in the choice bioassays. Females laid eggs indiscriminately on all four host types, and did not demonstrate host preferences. Our results provide important information for resource managers to consider when prescribing silvicultural mixes for planting. This is especially timely given the landscape-level reforestation following salvage harvesting associated with the current epidemic of mountain pine beetle in western Canada.