Efficacy of Match[registered sign] and Baycidal [registered sign] as insect growth regulators [IGRs] against adults of Culex pipiens L. mosquitoes

ABSTRACT

To evaluate the biological effects of two IGRs, Match [registered sign] and Baycidal [registered sign], on Culex pipiens mosquitoes, adults were fed on sugar solution mixed with 0.05, 0.25 and 0.5 ppm of each compound. Some delayed effects of these treatments were also determined. The results indicated that the use of the tested IGRs caused a reduction in the blood-feeding activity of mosquito females compared with the contrls. The reduction were 30.4, 39.1 and 47.8% when using Match and 36.9, 45.6 and 54.3% when using Baycidal [registered sign], respectively at corresponding concentrations. The reduction in biting activity of mosquito females may lead to a decrease in the number of fully engorged females and accordingly affect their reproductive capacity. The use of Match [registered sign] and Baycidal [registered sign] at tested concentrations caused a marked prolongation in the time needed for blood meal to be digested by C pipiens females. The prolongation percentages were 40.5, 69.0 and 71.4% when using Match [registered sign] and 61.9, 69.0 and 73.8% when using Baycidal [registered sign], respectively. Also, treatments caused a reduction in the reproductive capacity. The maximum decreasing in egg production was 34.5% at 0.5 ppm of Match [registered sign]. The result showed that the treatment by Baycidal [registered sign] at 0.05, 0.25 and 0.5 ppm led to a remarkable reduction in the egg production by 45.3, 49.3 and 55.9%, respectively, in addition, the hatchability was reduced in the treated females. A subsequent study was carried out to investigate the delayed effect of Match [registered sign] and Baycidal [registered sign] as IGRs on the newly emerged larvae. The result showed that the larval development was inhibited by 32.5, 58.0 and 89.8% when using Match [registered sign] at 0.05, 0.25 and 0.5 ppm, respectively. on the other hand the larval development was completely inhibited after the treatment of adults fed on 0.5 ppm Baycidal [registered sign]. The larvae developed till the 2nd instar but completely failed in molting to the 3rd instar. Subsequent study was conducted on the effect of Match [registered sign] and Baycidal [registered sign] on the longevity of the emerged mosquito adults, but not significant differences in the mean of adult longevity between treatments and control