Trichoderma spp. from roots of fumigated Douglas-fir trees infected with Phellinus weirii

Abstract

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

Key Words:

• chloropicrin
• fumigants
• methylisothiocyanate
• Pseudotsuga menziesii
• Trichoderma
• Vorlex