Larvicidal activity of Dregea volubilis and Bombax malabaricum leaf extracts against the filarial vector Culex quinquefasciatus

Objective: To analyze the larvicidal activity of two plant leaf powder and leaf extracts, Dregea volubilis and Bombax malabaricum against Culex quinquefasciatus. Methods: The larvicidal bioassay was done for powdered leaves of Dregea volubilis and Bombax malabaricum individually and their methanol extracts against first-, second-, third- and fourth-instar larval forms of Culex quinquefasciatus. Mortality rate was recorded after 24, 48 and 72 h of post exposure. LC50 and LC90 values were calculated at different time intervals for third instar larvae. Results: All the graded concentration (0.1%, 0.2%, 0.3%, 0.4%, 0.5%) of powdered leaves showed significant (P<0.05) larval mortality. The mortality rate was higher in 50 ppm doses of methanolic extracts of both the plants against Culex quinquefaciatus. The corresponding LC50 values were 56.97 ppm and 48.85 ppm, respectively after 24 h of exposure. There is no mortality of non target organism such as Chironomous circumdatus, Oreochromis niloticus niloticus and Diplonichus annulatum within 72 h of post exposure to 0.1%, 0.2%, 0.3% crude powdered leaves and methanolic extracts of both the two individual plants under the laboratory condition. The results of preliminary qualitative phytochemical analysis of both the plants revealed the presence of many bioactive principles such as steroids, tannins, flavonoids, triterpenoids, saponins, etc. that may be responsible for their bio-control potentiality. Conclusions: The results have shown potential and eco-friendly use of both plant extracts against larva of Culex quinquefasciatus for the first time.