Vol. 5, Issue 1, Part B (2018)

Author(s): MD Mahfuzur Rahman and Mohammad Tofazzal Hossain Howlader

Abstract: Two organophosphate (OP) insecticides (Chlorpyrifos and Fenitrothion) and one synthetic pyrethroid insecticide (Deltamethrin) were evaluated against 4^th instar larvae of Culex quinquefasciatus (Diptera: Culicidae) under laboratory condition. The larvae were collected from nearby area of Bangladesh Agricultural University, Mymensingh 2202 campus and reared at the Insect Biotechnology and Biopesticide Laboratory of Department of Entomology. For bioassay, five concentrations (viz. 10, 30, 50, 70 and 90ppm) of each of the insecticide were prepared. Ten actively swimming 4^th instar larvae of C. quinquefasciatus were added into respective concentration. Mortality was recorded and the LC₅₀ and LC₉₀ values were determined by probit analysis. The LC₅₀ values for Fenitrothion, Deltramethrin Chlorpyrifos, and were found to be 8.88, 26.73 and 71.14ppm, respectively. Thus, the Fenitrothion exhibited comparatively higher toxicity about 3 and 8 times more toxic compared to deltamthrin and chlorpyrifos. The order of the tested insecticides was found to be Fenitrothion > Deltamethrin > Chlorpyrifos. The LC₉₀ values were also followed similar trend. Hence, the Fenitrothion and Deltamethrin could be suggested for Culex mosquito larvae management.

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