Background : With respect to the importance of chemical control of malaria, the present study was conducted in order to evaluate the pirimiphos-methyl as a larvicide. In this respect, its stability, activity, and the interval between two treatments with pirimiphos-methyl were evaluated. This study was performed in artificial and natural breeding place at two villages in Kazeroon area.

Materials and Methods : It was an experimental study. Having prepared the artificial breeding places, they were sprayed by concentrations of 12.5, 20, 25, 40, 50, and 80 gr/ha. Meanwhile, temphos, reldan and pirimiphos-methyl were compared in concentrations of 25, 22.5, and 25gr/ha, respectively. Bioassay test was used to evaluate the poison stability.

Results: The recorded mortality rate for Anopheles larvae were 91.7, 99.7, 100, 100, 100, and 100%, respectively. Results have revealed there was a significant statistically difference between the concentrations of 12.5 and 20gr/ha of pirimiphos-methyl, however, this difference did not reach the statistical significant between concentrations of 20gr/ha and higher. Reldan has shown a great larvicide activity.

Conclusion : Temphos is quite safe but expensive, thus can not be widely used. On the other hand, Reldan is not biologically safe. Pirimiphos-methyl is a versatile, easy-to-handle, broad-spectrum insecticide of low toxicity to mammals. Further studies are needed to determine the rate of degradation of pirimiphos-methyl in natural breeding sites.