Reducing Phellinus weirii inoculum by applying fumigants to living Douglas-fir

• Published in: Canadian journal of forest research Vol. 26; no. 7; pp. 1158 - 1165
• Main Authors: Thies, W.G, Nelson, E.E
• Format: Journal Article
• Language: English
• Published: 01.07.1996
• Subjects: adverse effects; application rate; chloropicrin; disease control; fumigation; methyl isocyanate; mortality; nontarget effects; Phellinus weirii; phytotoxicity; plant diseases and disorders; Pseudotsuga menziesii; root rot; tree injection; Oregon
• ISSN: 0045-5067; 1208-6037
• DOI: 10.1139/x26-129

In 1982, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees were placed in three disease classes based on signs and symptoms of laminated root rot caused by Phellinus weirii (Murr.) Gilb. Eight fumigation treatments and an untreated check were applied to five replicate trees within each disease class. The dose applied to each tree was based on the estimated biomass in the belowground portion of the bole, large roots, and first 2.4 m of the aboveground bole. The highest dosages tested were 1.5 g of methylisothiocyanate (MITC), 6.7 mL of chloropicrin (trichloronitromethane), and 6.7 mL of Vorlex (v/v 20% MITC, 80% chlorinated C3 hydrocarbons)/kg biomass. In 1991 the roots of all surviving trees were excavated (roots of other trees were excavated at time of death), dissected, and sampled for viable Phellinus weirii. Twenty-four of the 30 trees treated with the two highest dosages of chloropicrin were killed, presumably by the fumigant. None of 45 trees treated with MITC and only 3 of 15 trees treated with Vorlex died, as did 3 of 15 untreated check trees. Volume of stained and decayed roots occupied by viable Phellinus weirii was reduced 78-90% by MITC or Vorlex compared with reductions of 51-65% by chloropicrin at the two lower, less phytotoxic doses, and 9% for untreated checks.