DECOMPOSITION OF BALSAMID IN DOUGLAS-FIR HEARTWOOD - LABORATORY STUDIES OF A POTENTIAL WOOD FUMIGANT

Basamid dimethyl-1,3,5,2H-tetrahydrothiadiazine-2-thione), a crystalli ne powder first used as a soil sterilant, has shown promise as a wood fumigant. This chemical decomposes to methylisothiocyanate (MITC), the primary active ingredient, as well as other products; but the rate of decomposition in wood is too slow to be effective unless certain cata lysts are used. This study explored conditions and additives that acce lerated Basamid decomposition in Douglas-fir heartwood. MITC productio n increased with increasing temperature and moisture content. Decompos ition was also enhanced by a buffer powder formulated to reach pH 12 w hen mixed with 100 ml of water and, more efficiently, by copper sulfat e. Carbon disulfide, a less fungitoxic compound, was the only other de composition product detected in this study. Additional tests using a p urge-and-trap system indicated that MITC was produced at a steady, mod erate rate over a 28-day period. Addition of copper as a catalyst in t hese tests increased MITC production only during the first 7 days. Che mical analyses of residues at the conclusion of the tests indicated th at most of the Basamid remained unchanged, providing a reservoir of ch emical that should provide long-term MITC release.