Host range, attack dynamics, and impact of Cryptorhynchus lapathi (Coleoptera : Curculionidae) on Salix (Salicaceae) spp.

The poplar and willow borer, Cryptorhynchus lapathi (L.), known to be prese nt in British Columbia since 1923, primarily attacks species of Salix L. (S alicaceae) and Populus L. (Salicaceae). Larvae bore into stems, causing the m to break easily. The impact of the weevil has been rising in recent years because of the increasing importance of poplar and willow from bath econom ic and ecological perspectives. We conducted a study at 45 locations in Bri tish Columbia to determine host use among native Salix spp. and the between - and within-tree dynamics of C. lapathi. There were 11 new host records, b ut the incidence of attack was similar among species. Attacked trees were l arger in general and had more dead wood and stems, more adventitious branch es per stem, more total breaks per stem, and more naturally caused breaks p er stem than their attack-free neighbours. Breaks caused by C. lapathi tend ed to be slightly larger in diameter and lower on the stem than naturally c aused breaks. Bases of stems were preferentially attacked, and C, lapathi s elected large stems in which to oviposit. As large attack-free trees become less abundant, weevils apparently start to attack small-diameter stems. Al though C. lapathi is adversely affecting the health of willows in British C olumbia, there is no evidence that any Salix species is threatened by weevi l-caused extinction.