Larvicidal potentential of four plants extacts against Culex quinquefasciatus
The larvicidal activity of Polygonum glabrum extract against 2nd, 3rd and 4th instar larvae of Culex quinquefasciatus was evaluated at concentrations of 100 ppm, 200ppm and 400 ppm. The larvicidal activity of Mallotus philippensis, Citrus aruntium and Fumaira officinalis was studied at concentrations of 40ppm, 80ppm and 120ppm. The physical characteristics of distilled water used for the study like temperature 21°C-28°C , pH ( 7 -9) , Dissolved oxygen 2- 3 mg /l .The larval mortality was assessed after 12, 24 and 36 hrs , exposure and LC50 and LC90 were calculated for each plant extract and at each time interval . Among solvent extracts studied, the maximum efficacy was observed in the ethanol extracts of P.glabrum and M.philippensis. The average moratlity after 12 hr against 2nd, 3rd and 4th instar larvae of Culex quinquefasciatus was 15.00±0.00, 15.00±0.00, 15.00±0.00 and 8.33±2.30, 11.33±0.57, 10.16±1.72 in ethanol extract of Polygonum glabrum, Mallotus philippensis respectively at concentration used in this experiment. Similarly average mortality caused by ethanol extract of Polygonum glabrum after 24 and 36 hr was noted as 15.00±0.00, 15.00±0.00, 15.00±0.00 and 15.00±0.00, 15.00±0.00, 15.00±0.00 respectively at concentration 400ppm. The average mortality caused by ethanol extract of Mallotus philippensis against 2nd, 3rd and 4th instar larvae of Culex quinquefasciatus after 24 and 36 hr was 10.33±0.57, 11.66±0.51, 10.83±1.47 and 15.00±0.00, 13.33±1.86, 13.33±1.86 respectively at concentration 120ppm.
While C.aruntium and Fumaira officinalis did not show effective larvicidal activity. No mortality was observed in control. These plants extracts are therefore promising as an alternative to synthetic insecticide mosquito control programmed. Thus providing the basis to use the plant extracts against C. quinquefasciatus (Culex fatigans).It can be concluded from the present study that the ethanol extracts of P.glabrum and M.philippensis possess active compounds and can be used for the development of larvicides from plant resources.