Effect of Swiss needle cast on Douglas-fir stem ethanol and monoterpene concentrations,oleoresin flow,and host selection by the Douglas-fir beetle

摘要

Douglas-fir growing on the western slopes of the Oregon Coast Range are experiencing an unprecedented outbreak of Swiss needle cast (SNC) caused by the fungus Phaeocryptopus gaeuman-nii.SNC can produce substantial physiological stress in host trees by reducing needle gas exchange and enhancing premature needle abscission,resulting in slower growth.Based on the frequent link between stressed trees and insect activity,we explored the potential influence of SNC on Douglas-fir beetle,Dendroctonus pseudotsug-ae,activity and some tree physiological parameters that may influence beetle attraction (i.e.,constitutive ethanol and monoterpene contents of woody tissues) and host susceptibility (i.e.,wound-induced resin flow).