Permeability of plastic films to methyl bromide: field study

The use of gas-impermeable films to minimize methyl bromide (MB) emission into the atmosphere from soil fumigation was studied in the field. Three experiments evaluated various plastic films during fumigation with a reduced dosage of MB. The concentration of MB decreased sharply in the soil during the first 24 h when polyethylene-based films were used. In contrast, films having a layer of barrier material, such as polyamide or ethylene vinyl alcohol, were significantly less permeable, shown by a gradual decrease in the MB concentration in the soil, a relatively higher concentration in deeper soil layers, and higher concentration (C) by exposure time (T) (C x T) values. A significant correlation was obtained between permeability values obtained in the laboratory and C x T values in the field. Fumigation under impermeable films at the reduced dosage of 20-25 g m(-2) was effective in killing propagules of five pathogenic fungi to a depth of 40 cm. The significant correlation obtained between C x T values and the level of fungal killing suggests that using impermeable films reduces MB dosage and emission to the atmosphere while maintaining effective pest control. (C) 1998 Elsevier Science Ltd. All rights reserved.