LARVICIDAL POTENTIAL OF SEAGRASS EXTRACTS AGAINST DENGUE VECTOR AEDES AEGYPTI (INSECTA: DIPTERA: CULICIDAE)

Abstract

The present study was made an attempt to identify the larvicidal activity of the seagrass extracts. Four seagrass species and different plant extract (leaf and root) viz., Halophila ovalis (AUOCAS025), Enhalus acorodies (AUOCAS026), Thalassia hemprichii (AUOCAS027) and Halodule pinifolia (AUOCAS028) were tested against A. aegypti mosquito larvicidal activity. Batches of 25 early 4^th instar larvae of A. aegypti were transferred to 250ml enamel bowl containing 199ml of distilled water and 1ml of plant extracts (0.01mg-0.1mg). Each experiment was conducted with three replicated and a concurrent control group. A control group consisted of 1ml of DMSO and 199ml of distilled water only. The larvae were considered dead  at the end of 24 hrs and the percentage of mortality was  determined with the formulae with % of test mortality -% of control mortality/100-% of control mortality X100. The extract of H. ovalis showed maximum larvicidal activity (LC₅₀ value 0.067±0.007 μg.ml^-1 and LC₉₀ value = 0.128±0.025 μg.ml^-1) followed by leaf extract of E. acorodies (0.0852 ± 0.006 μg.ml^-1 and LC₉₀ = 0.1369±0.036). Similarly no mortality was found in extracts of T. hemprichii (leaf) H. pinifolia (leaf) showed no mortality of 4^th instar larvae of A. aegypti. It is concluded from the present study that, the ethanolic extract of seagrass  H.ovalis possesses and they can be developed as lead compounds for mosquito control.