Vol. 2, Issue 2, Part A (2015)

Author(s): T.P.N. Hariprasad, A.B. Arun

Abstract: Anopheles stephensi, an important Indian urban malaria vector was collected from Thokottu locality of Mangalore, India. Larval bioassays were carried out according to the procedure of WHO for evaluating the resistance levels to six insecticides and two plant extracts. The insecticides include alphamethrin, cypermethrin, fenvalerate lambda cyhalothrin, chlorpyrifos and propoxur. The plant extracts were methanol and hexane extracts of Eucalyptus globulus and Calotropis gigantea. Anopheles stephensi was found to be susceptible to alphamethrin (LC₅₀ = 0.042 mg/L) and resistant to lambda cyhalothrin (LC₅₀ = 1.99 mg/L). Among the plant extracts, hexane extracts of Eucalyptus globulus and C. gigantea were found to be effective (LC₅₀ = 314.26 and 311.67 mg/L respectively) than methanol extracts. Additionally egg morphometry was carried out. The mean (M±SE) egg length and width were 488.01± 6.28mm and 169.9mm ± 3.30mm respectively. Based on the egg float ridge number, Thokottu strain was classified as Type form with 19-21 ridges.

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