Bioassay of Larvicidal Efficacy of Selected Plant Extracts Against Mosquito Larvae Anopheles Culicifacies and Aedes Aegypti L.

Abstract

Mosquitoes act as a vector and are the most significant  nuisance for spreading many diseases, viz. malaria,  dengue and filariasis encephalitis. The extensive use of  chemical insecticides to control these vector-borne  diseases causes adverse environmental impacts, pest  resurgence, vertebrate toxicity, and physiological  resistance to vectors. The present research work was  undertaken to study the efficacy of ethanolic extracts of  commonly available plants, viz. Paederia foetida, Murraya  koenigii, Zingiber officinale and Allium sativum against the  larvae of the mosquitos, Aedes aegypti and Anopheles  culicifacies at different sub-lethal concentrations (50 mg,  100 mg, 150 mg per 100 ml of water) for 1 hour, 10  hours, 24 hours, 48 hours, 72 hours and one week of  exposure. The study was based on the behavioural  changes, mortality rate and larval development  following standard technique. The phytochemical  screening for these plants was carried out following  standard methods. The investigation results showed  abnormal changes in the behaviour, such as hyperactive  wriggling movement in the initial period. In contrast,  sluggish and motionless movements were also observed  in the later days of exposure associated with an upward  mouth posture on the water surface indicative of the  moribund condition. The impairment of the larval  development and attainment of fly size was also noted  in that they respond variedly to the different plant  extracts in a dose and time-dependent manner. The  mortality rates in these two mosquito larvae with  respect to these plant extracts have also recorded an  increasing trend, i.e., A. sativum> P. foetida> Z. officinale>  M. koenigii.