| Abstract: | Experimental fumigations of cased tobacco with methyl bromide to control the Cigarette beetle (Lasioderma serricorne) were conducted at low temperatures. Two stowages, each of 120 × 181 kg cases, were built and made gas-tight with seamless polyethylene film. Methyl bromide was introduced into each stowage at a concentration of 64 g/m3. Gas concentrations were monitored at a depth of 15 cm into the tobacco and at the centre of cases. Six cases (two open, two with folded polyethelene liners and two with heat-sealed polyethylene liners) were sampled in each stowage. Good penetration was achieved when atmospheric temperatures ranged from 6.5 to 8.5°. It is concluded, therefore, that tobacco fumigations with methyl bromide may be carried out satisfactorily in cold weather, providing that temperatures do not fall to a level at which insects become highly tolerant to the fumigant. However, amounts of fumigant reaching the centre of the heat-sealed cases were insufficient to ensure the effectiveness of such treatments in all situations. It is recommended, therefore, that the procedure of slitting polyethylene liners of heat-sealed cases before fumigation be continued. |
