Remedial treatment of Douglas-fir and southern pine poles with methylisothiocyanate

The effectiveness of glass-encapsulated methylisothiocyanate (MITC-Fume?) as a fumigant compared to metham-sodium was examined in Douglas-fir and southern pine poles, over a 3-year period, with fungal bioassays and chemical analysis. MITC release from small Douglas-fir pole sections treated with 30 g MITC-Fume was highly temperature dependent, with the fastest movement occurring at higher temperatures (32?C) and extremely slow movement occurring at low temperatures (5?C). In field trials using full-scale poles, MITC movement was slightly better in Douglas-fir than in southern pine, despite the latter’s higher permeability. Fungal bioassays revealed that with the MITC-Fume treatments, MITC migrated in both wood species up to 0.9 m form the highest application point over a 3-year period. Residual MITC levels increased over the first 2 years, then declined in the third. In general, poles of both species treated with metham-sodium contained lower levels of residual MITC than poles treated with MITC-Fume, which reflects the inefficient decomposition of metham-sodium. The results indicate that MITC-Fume performance exceeds a 500-ml metham-sodium treatment, even at the lowest dosage evaluated (60 g).

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