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Paper Details

Toxicity of Cypermethrin and Malathion on Rice Weevil Sitophilus oryzae (L.) and Their Effect on Esterase Isozymes

Md. Hasan Iqbal, Md. Abdur Rashid*, Rowshan Ara Begum and Reza Md. Shahjahan

Journal Title:Journal of Chemical, Biological and physical sciences

Experiments were conducted to study the toxicity and esterase isozyme pattern in rice weevil (Sitophilusoryzae), a major pest of the stored rice. Bioassay was conducted with cypermethrin and malathion against the adult weevils and LC50 was found to be 110.30 ppm and 12.19 ppm respectively at 24 hours of exposure. Malathion was found to be much more toxic to S. oryzae than that of cypermethrin. In general, the mortality increased with an increased dose and with the time of exposure. Altogether, four esterase bands (Est-11.36 ,Est- 20.99, Est-30.45 and Est-40.24) were detected on 7.5% polyacrylamide gels with ? naphthyl acetate as substrate. Changes of esterase isozyme due to cypermethrin and malathion treatment was also observed. Est-1 was appeared only in the cypermethrin treated dead samples of 3-9 days of exposure, which was found highly intense after 5 days and the intensity gradually decreased afterwards. Esterase activity in malathion killed samples decreased with the increase of exposure period and with dose concentrations in general, however, fluctuation in esterase activity was found in cypermethrin killed samples.