REDUCTION OF PHELLINUS-WEIRII INOCULUM IN DOUGLAS-FIR STUMPS BY THE FUMIGANT TELONE-II-B

Two dosages of Telone II-B (1,3-dichloropropene) at 3.4 and 6.7 mL/kg of stump and root biomass were tested to determine the efficacy in red ucing Phellinus weirii (Murr.) Gilb. inoculum in infected Douglas-fir, Pseudotsuga menziesii (Mirb.) France, stumps. After 21 months, both d oses of Telone II-B proved equally effective and significantly (p < 0. 05) reduced residual P. weirii mycelium in infected roots. Fumigation reduced residual endotrophic P. weirii in the large-diameter root clas ses nearest the stump, but survival of the fungus was less affected wi th increasing distance from the stump and in the smaller root diameter classes. Treated stumps also had significantly (p < 0.05) fewer roots with ectotrophic mycelium than untreated stumps. Four weeks after app lication, soil samples taken near treated stumps revealed no evidence of the fumigant. These findings suggest that application of Telone II- B could be used as an effective control measure for P. weirii.