Evaluation of mosquito larvicidal activity of Azolla pinnata leaf extracts against the filarial vector Culex quinquefasciatus

Bhattacharjee, Indranil ; Mandal, Biplab ; Chakravorty, Partha Pratim

Abstract

Vector control is a major challenge now-a-days when they became resistance against commonly available insecticides. As an alternative, preliminary laboratory evaluation of Azolla pinnata crude and chloroform: methanol solvent extract was carried out under laboratory trials for control of Culex quinquefasciatus. Crude and solvent extract (chloroform: methanol) extracts of A. pinnata leaves were examined for the larvicidal activity against all the larval instars (1st to 4th) of C. quinquefasciatus. Dose-dependent mortality assays were performed using the extracts. Further, determinations of LC50 and LC95 values were accomplished through log-probit analyses and regression analyses. The larvicidal activity was statistically justified through ANOVA analyses. Effects of the extracts were examined on non-target water fauna. Exposure to A. pinnata crude and chloroform: methanol extract increased the mortality of first to fourth-instar C. quinquefasciatus. All the graded concentrations showed significant (P <0.05) larval mortality and the results of the regression equation revealed that the mortality rates were positively correlated with the concentrations of the extracts (R2 close to 1). LC50 values of all instars after 24 h of exposure were between 86.99-294.06 ppm for crude and 48.87-111.44 ppm for chloroform: methanol extract. Chloroform: methanol extract is better than crude because the nature of biological components can be enhanced in presence of solvent and secondly the stronger extraction capacity could have produced a greater number of active constituents. The residual effect is noted even at the end of 72 h. A negligible toxicity to the larvae of Chironomus circumdatus was noticed as non-target organisms.


Keyword(s)

Azolla pinnata; Culex quinquefasciatus; Larvicide; Leaf extract; Non-target organisms.

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