Artificial Inoculation of Decay Fungi into Douglas-Fir with Rifle or Shotgun to Produce Wildlife Trees in Western Oregon

Abstract

Abstract A total of 188 Douglas-fir trees were treated to determine whether fungal inoculation with rifle or shotgun promoted stem decay and subsequent use by cavity-nesting birds in the Coast Range in Oregon. Inoculated trees were either live or killed by topping. Topped trees were climbed and severed just below the lowest whorl of live branches. Fungal inoculum was delivered by either a 0.45–70 caliber rifle or a 12-gauge shotgun to tree trunks at a height of about 8 m aboveground. Inoculum of either Phellinus pini or Fomitopsis cajanderi was grown on small wooden dowels or sawdust and fitted into the rifle slug (dowels) or behind the shotgun slug (sawdust). Sterile dowels or sawdust were used as a control. After 5 years, all topped trees had died, and at least 50% had sap rot as indicated by the presence of conks of Trichaptum abietinum. Conks of Crytoporus volvatus, Fomitopsis pinicola, or P. pini were sometimes observed on topped (dead) trees. Almost half of the topped trees had evidence of wildlife activity including foraging holes, nest cavities, or bark removal. There was no difference in sap rot incidence or subsequent wildlife activity among three treatments (rifle, shotgun, or not shot) or among three inoculum types (P. pini, F. cajanderi, or sterile). None of the untopped (live) but artificially inoculated trees had conks or evidence of wildlife use. Of seven live and shot trees that were destructively sampled, there was an average of 68.7 cm2 of decay area on each wood disc that was associated with each bullet. There was no apparent difference in internal decay area between sterile and viable inoculum, but sample size was small. It appears that tree killing by topping below the live crown is a faster method of creating wildlife habitat than ballistic inoculation of live Douglas-fir trees in the Oregon Coast Range. Topped and dead trees had more avian foraging holes, deep cavities, and bark removed than did live inoculated trees. Based on the seven live shot trees that we sampled for internal decay, it appears that shooting trees with a shotgun or rifle is effective in creating internal decay within 5 years, but it may take several more years to form a decay column large enough to be used by cavity-nesting birds. West. J. Appl. For. 19(3):211–215.