The response of Musca domestica (L.) in farms sprayed for long periods by organochlorine to synthetic pyrethroids.

Resistance ratios for Musca domestica collected from animal farms and poultry units, sprayed by organochlorine insecticides for long periods and standard laboratory strain were determined. The data indicated high significant resistance in animal farms population to organochlorine compounds and cross-resistance to synthetic pyrethroids. The organochlorine resistant and standard laboratory strains were examined for knockdown and rate of penetration to two synthetic pyrethroids. Standard laboratory strain was knocked down within few minutes by lower or higher dosages. Resistant strain was unaffected by lower dosages within 24 hours and partly by higher dosages. Penetration was faster in the resistant than in the standard strain. However, significant differences did not occur until after the standard laboratory females become moribund. The higher penetration rate in the resistant housefly adults was attributed to their continued activity throughout the exposure periods.