The influence of wood moisture content on the fungitoxicity of methylisothiocyanate in Douglas-fir heartwood

High concentrations of the fumigant methylisothiocyanate (MITC) will effectively control decay fungi in large wood structures, but the fungitoxicity of low MITC concentrations and the influence of wood moisture content (MC) on its performance are not well understood. The MC of Douglas-fir heartwood greatly influenced the susceptibility of the decay fungus Poria carbonica to MITC vapors and the amount of MITC adsorbed by the wood. At constant, low MITC vapor concentrations (less than 1 ug/cc air), wood at 10% MC adsorbed 5 times more MITC, but required 4 times the exposure period to control P. carbonica, than wood above the fiber saturation point. Adsorption of MITC to wood was not substantially influenced by the amount of wood decay. When wood MC was raised from 10% to 30% during fumigation, previously adsorbed MITC rapidly volatilized and fumigant fungitoxicity increased