Effectiveness of insecticides, physical barriers and size of planting stock against damage by the pine weevil (Hylobius abietis)

A series of five trials was established in Great Britain to test the effectiveness of fourteen treatments and a control on reducing mortality and damage by pine weevil (Hylobius abietis) on recently replanted Sitka spruce (Picea sitchensis). Overall percentage mortality and damage was significantly different between trials, varying from a median of 24%–100%. The most effective treatments in reducing mortality were insecticides and physical barriers, with insecticides being most cost effective. Low volume applications of insecticides were found to be as effective as higher doses. Using larger trees did not reduce mortality compared to the control, nor did application of a controlled release fertiliser. At Auchencairn, the trial where mortality was highest no treatment provided protection and so there is a need to develop an effective and integrated approach to reducing damage by pine weevil.