A Note On The Sensitivity of A Closed-Tube Bioassay To Volatile Methylisothiocyanate Residues In Fumigant-Treated Wood

A closed-tube bioassay with Poria placenta was used to measure residual fungistatic vapors in wood fumigated with methylisothiocyanate (MIT). This bioassay showed an inverse linear relationship between fungal growth and the amount of MIT in the wood samples. For fumigated increment-core sections of unseasoned Douglas-fir heartwood (4.8 mm in diameter by 25 mm long), the sensitivity of the bioassay ranged from 2 to 10 μml MIT per section. Closed-tube-bioassay response was also determined for small slivers of seasoned ponderosa pine and Douglas-fir, and was influenced by the size of the samples