Vol. 3, Issue 6, Part A (2016)

Author(s): Olorunfemi O Sunday, Akinwande Kayode L and Ashamo MO

Abstract: Mosquitoes constitute the largest human disease vectors, which spend their adult life indoor and outdoor while the juvenile stages live in aquatic environment. This research reviews the sublethal effects of Cypermethrin on biology of Culex quinquefasciatus Say. Insects that survive lethal concentrations have been impacted with a sublethal dose which might not produce immediate mortality but have a prolonged effect on the biology and body biochemistry. Laboratory analyses was carried out with LD₁₀, LD₂₀ and LD₃₀ of cypermethrin at a temperature of 27-29 °C, relative humidity of 70-85% and photoperiod of 14:10 (L: D) and acetone was used as a chemical control. The mosquitoes were caged and provided with 10% sucrose syrup and blood meal. The percentage of adult emergence from the 4th instar larval of the mosquito were significantly different for all the sublethal concentrations and control (F (3, 19) = 167.568, p = 0.000). Mean rate of oviposition decreases from the Control = (107.20±3.02), LD10 = (104.40±2.82), LD₂₀ = (93.67±2.69) and to LD₃₀ = (87.00±2.19). The mean life span by the adult female decreases from 12.44+0.193 in the control to 7.20+0.109 at LD₂₀ and the decrease were significantly different (F (3, 19) = 226.149, p = 0.000). In view of the environmental modifications that have impacted on our ecosystems and insect populations, there is a need to constantly review the lethal and sublethal effects of many insecticides as this will help to determine the dose response-status of insect vectors for prioritization and design of chemicals for control programmes.

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