EFFECT OF CHANGES IN TEMPERATURE ON SYNERGISTIC TOXICITY OF CYPERMETHRIN AND DDVP ON Culex quinquefasciatus (DIPTERA : CULICIDAE)

Abstract

The research investigated the effect of temperature on the toxicity of cypermethrin and Dichlorvos on (Culex quinquefiastus). The insects were reared under laboratory condition and exposed to different concentrations of the two insecticides at varying temperatures (270C, 320C and 370C). Furthermore, the two insecticides were also combined to determine the antagonistic /synergistic toxicity under varying temperature. Mortality was recorded at 30, 60 and 90 minutes of exposure. Data obtained were analyzed using probit and logit and analysis of variance were used to test the level of significance in the susceptibility of Culex quinquefiastus to changes in temperature and time of exposure. Cypermethrin, showed fluctuation in toxicity with changes in time of exposure, at 30 and 90 minutes. The highest toxicity was recorded at 370C while at 60minutes, the highest toxicity was recorded under 320C. DDVP toxicity increases with increase in time and temperature with optimum toxicity recorded at 37oC. The mortality value obtained from the combination of the two insecticides was higher compared to when used singly. The study revealed a synergistic relationship between cypermethrin and DDVP. The study showed that in addition to temperature, potency of two insecticides. Hence, the choice of insecticides, appropriate dosage and prevailing environmental conditions are important function in effective mosquito control.