An Accelerated Test Method for Evaluating the Performance of Wood Pole Fumigants

Dazomet (tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione) is a solid fumigant that breaks down into gaseous methylisothiocyanate (MITC) in the presence of water, a process that can be enhanced by the addition of accelerant chemicals. Experiments to discover the ideal conditions for dazomet decomposition were largely performed at the lab scale or on field-scale full utility poles or sections thereof. A rapid assessment method in wood commodities would improve the ability to assess a wider range of treatments to improve performance. Here, we present a method to test dazomet performance at the mesocosm scale in 102 × 152 mm (4 × 6-inch nominal) lumber. The protocol was trialed using two EPA-registered dazomet formulations to produce MITC under varying moisture conditions using different copper-containing accelerants. The test allowed the assessment of MITC levels at different locations and the full visual inspection of the treatment hole after splitting the block. MITC levels tended to be higher in the wood interior, closer to the treatment holes in test blocks. Below-ground portions also tended to have higher MITC levels at higher-moisture conditions. The method developed reduces the time required to test dazomet formulations and application methods in whole wood and will help improve the development of new dazomet formulations and application methods.