Biological and histopathological studies of some plant extracts on larvae of Culex pipiens (Diptera: Culicidae).

The water extract of Artemisia monosperma, Eichhornia crassipes and Zygophyllum coccineum was tested against the 2nd instar larvae of Culex pipiens and the resulting pupae and adults. The larvae were exposed to serial concentrations (0.5, 1.0 and 2.0%). All extracts showed marked effects on larval mortality, pupation and adult emergence as compared to the non-treated group. These effects were dose (concentration) dependant (P < 0.001). The results indicate that the water extract of E. crassipes gave marked and significant effects, followed by A. monosperma and Z. coccineum particularly at 2% concentration (P < 0.001). The water extract of E. crassipes at 2% conc. revealed drastic effect on larval midgut, integument, fats and muscles. These histopathological effects increased with increasing the time of exposure (treatment).