The requirement for the inclusion of formulation efficacy trials in pesticide preregistration evaluations

Optimization of biocide use could serve to reduce the risks of biocides on human health. To optimize the risk/benefit ratio, it is important to develop procedures for evaluating the efficacy of biocide formulations. The authors examined the effectiveness of ten pyrethroid insecticide aerosol formulations registered for the household control of flies. Tests were performed using adult Musca domestica L. Knockdown effects and mortality were measured in a test chamber using the manufacturer's recommended discharge time.

The knockdown effect varied greatly between aerosols of similar composition. The knockdown 15 min post-treatment was 66-98% for flies placed 120 cm above floor level and 53-96% for flies placed at a height of 180 cm. The KDT(50) values ranged from 2.5 to 9.2 min for flies placed at 120 cm and from 3.2 to 12 min for flies placed at 180 cm. The highest rates of mortality were obtained for a formulation containing S-bioallethrin, permethrin and piperonyl butoxide (81% at 120 cm and 79% at 180 cm).

Formulations similar in insecticide composition exhibit significant differences in efficacy. Consequently, insecticidal efficacy preregistration evaluations should address not only the efficacy of the active ingredient but also the effectiveness of the formulation.