Larvicidal and Histopathological Effects of Cassia siamea Leaf Extract against Culex quinquefasciatus

A traditional Thai medicinal extract from Cassia siamea was evaluated with respect to its larvicidal properties by determining the median lethal concentration (LC50) at 24, 48, 72 and 96 h against the fourth instar larvae of Culex quinquefasciatus, which is a carrier of mosquito-borne diseases, by studying the histopathological alterations. The 24, 48, 72 and 96 h LC50 values were 394.29, 350.24, 319.17 and 272.42 ppm, respectively. The histopathological lesions after exposure to 25% of the 24-h LC50 were observed primarily in the midgut of the larva. Lesions with edema, swelling, and deformation or elongation of the epithelial cells were observed. Moreover, cells protruding into the lumen and absent microvilli were also found in some areas. The present study reveals that aqueous C. siamea leaf extracts have natural biopesticide properties.