TRICHODERMA SPP FROM ROOTS OF FUMIGATED DOUGLAS-FIR TREES INFECTED WITH PHELLINUS-WEIRII

Seven species of Trichoderma were isolated from roots of 104 live Doug las-fir (Pseudotsuga menziesii) trees infected with laminated root rot caused by Phellinus weirii. The trees were treated 10 years earlier w ith one of three fumigants: Vorlex, methylisothiocyanate, or chioropic rin. Sample chips from root sections appearing to be stained or decaye d by P. weirii were plated on malt agar. Most (73%) of the Trichoderma spp. isolated were T. viride. Though not tested statistically, Tricho derma spp. were isolated more often from fumigated trees than from non fumigated trees. In root sections of nonfumigated trees, Trichoderma s pp. were isolated significantly less often where P. weirii was viable than where it was not.