Larvicidal potentential of four plants extacts against Culex quinquefasciatus

Mosquitoes remain the important group of insects in terms of public health importance. They spread a number of diseases such as filariasis, malaria, Japanese encephalitis etc., causing millions of death every year.  Natural products of plant sources with insecticidal properties have been used for control of a diversity of pest insects and vectors. The present study is focused on evaluation of the larvicidal activity to determine the efficacies of ethanol extracts using plant parts of Polygonum glabrum, Mallotus philippensis, Citrus aruntium and Fumaira officinalis against 2^nd, 3^rd and 4^th instar larvae of Culex quinquefasciatus (earlier name: Culex fatigans, (Diptera: Culicidae).The ethanol extracts; of leaves of P.glabrum, C.aruntium, seeds of M.philippensis,complete plant without roots of Fumaira officinalis were obtained using Soxhlet apparatus with Ethanol as solvent. The stock solution of each extract was prepared by evaporating the solvent using Rotary Evaporator. Different concentrations of each extract were prepared by dissolving 1 gm of each solid extract in 100 ml water.

The larvicidal activity of Polygonum glabrum extract against 2^nd, 3^rd and 4^th 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 2^nd, 3^rd and 4^th 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 2^nd, 3^rd and 4^th 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.