Aspects of host selection behaviour of Pissodes strobi (Coleoptera: Curculionidae) as revealed in laboratory feeding bioassays

Abstract

Both sexes of prewintering P. strobi adults preferred to feed on Sitka spruce lateral branch sections of larger diameter when presented a choice of two sections from the same current-year host lateral. In choice bioassays, both sexes preferred to feed on Sitka spruce rather than western hemlock or western red cedar. Females preferred to feed on Sitka spruce rather than Douglas-fir, whereas males did not discriminate. When presented either Sitka spruce or one of the three nonhost species alone, both sexes fed equally on Sitka spruce, Douglas-fir, and western hemlock. Neither sex fed on western red cedar, and weevils were seldom observed in contact with this species. Both sexes preferred to feed on Sitka spruce sections soaked in water rather than on those soaked in cedar exudate, suggesting that cedar contains repellents and (or) feeding deterrents. Sustained feeding by both sexes on pith discs containing a 50% ethanol extract of Sitka spruce leader bark suggests that Sitka spruce bark contains feeding stimulants. As only female P. strobi exhibit a feeding response that is dependent on the concentration of applied extract, females may have a more prominent role than males in host-tree selection during spring dispersal.