A large-scale field trial of ultra-low-volume fenitrothion applied by a portable mist blower for the control of Aedes aegypti.

Long-term control of Aedes aegypti, the vector of dengue haemorrhagic fever in Thailand, was obtained by 2 thorough applications of fenitrothion mist applied at a target dosage rate of 0.1 ml per m(3) of room space. Perfect control lasted for 6-7 months after treatment and densities were substantially reduced for up to a year after treatment. Recovery of the population was still slow up to almost 16 months after treatment. This degree of control was achieved by the immediate mortalities produced by 2 treatments spaced about 2 weeks apart, the larvicidal effect of the fenitrothion aerosol, and a limited residual effect that prevented oviposition for a period, so that the recovery potential was greatly diminished. It appears that aerosol and mist treatments designed as epidemic control measures can be adapted to long-term preventive control of A. aegypti. However, the equipment used and the method of application require further improvement.