Results of spraying with ultra-low-volume malathion at ground level in Panama City.
Several ultra-low-volume (ULV) sprayings of technical malathion (95 per cent) were carried out in Panama City. Their purpose was to find out how useful this ULV technique could be in helping to combat mosquitoes, especially Aedes aegypti. Two residential areas were selected as sites for the trials. One of these was San Francisco, a district near the shoreline of the Bay of Panama with many individual houses and a few tall buildings. The other was El Cangrejo, a district further inland containing numerous multi-story apartment buildings and several luxury hotels. Two trials were conducted in San Francisco, both involving a single application of insecticide. One of these tested the effect of street spraying on mosquitoes and larvae left inside and outside of one and two story dwellings, while the other involved similar testing of the effects on ten floors of a high-rise apartment building. There was only one trial in El Cangrejo, but this employed three applications of insecticide at two-day intervals. Like the second San Francisco trial, it tested the effect of the spray on mosquitoes and larvae left in a high-rise apartment building. All the mosquitoes used were obtained from the insectarium of the National Malaria Eradication Service. A. aegypti adults and larvae and Anopheles albimanus larvae were used in the first San Francisco trial. Thereafter, because available supplies of A. aegypti were exhausted, An. albimanus adults and larvae were used alone. The results of these trials were very satisfactory. All adult mosquitoes were killed in most cases, the only exceptions being mosquitoes exposed to a single application that was made under adverse conditions. Fairly high rates of larval mortality were also obtained. Overall, the results strongly indicate that thrice-weekly ground-level ULV spraying with malathion can serve as a highly effective mosquito control measure.