FIELD TRIAL OF CARBONYL SULFIDE FUMIGATION OF HAY IN 40FT SHIPPING CONTAINERS

The fumigation of bales of oaten hay for export poses a challenge to successful fumigation. They are very highly compressed, each measuring 500mm x 460mm x 360mm and weighing 64kg. Traditionally, shipping containers packed with these bales have been fumigated with methyl bromide to meet the phytosanitary requirements of importing countries. Alternatives currently available (phosphine and carbon dioxide) require long exposure times (7 days and 15 days respectively) and are recommended only if the ambient temperature exceeds 15°C. Carbonyl sulfide (COS) offers a faster alternative to either of these fumigants. Insect mortality studies indicate that a dose of 60 gm-3 COS for 48 hours will kill more that 99 % of the hardest to kill life stage of Sitophilus species at temperatures above 17°C (Weller and Morton, 2001). Below 17°C a longer exposure time is required to achieve the same level of kill given the same concentration, for instance, at 10°C a 4 day exposure of 60 gm-3 would be needed. In a field trial, 60 gm-3 COS (calculated on the empty vessel) was applied to oaten hay in a 40ft shipping container (76.4m-3) with an 8 second pressure halving time (empty). Penetration of gas into the bales and diffusion out of the bales during airing was assesse