OVIPOSITION DETERRENCE AND ADULT EMERGENCE INHIBITION ACTIVITIES OF CYMBOPOGON NARDUS AGAINST CULEX QUINQUEFASCIATUS WITH STUDY ON NON-TARGET ORGANISMS

The present study aimed to investigate the oviposition deterrent and adult emergence inhibition activities of non-polar solvent extract of Cymbopogon nardus whole plant against Culex quinquefasciatus mosquito with effect on non-target organisms. During the oviposition deterrent activity, the 1000 ppm concentration of extract showed maximum (71.9 +/- 3.3 %) effective repellence (ER). The lowest concentration (31.25 ppm) caused 13.4 +/- 1.3 % ER. The oviposition activity index (OAI) of the gravid female Cx. quinquefasciatus was estimated. For each concentration, negative OAI value was found. The negative OAIs values indicated that the n-hexane extracts of C. nardus whole-plant is oviposition repellent. Lowest OAI value was exhibited by 1000 ppm extract solution. During the adult emergence inhibition (EI) activity, the C. nardus n-hexane extract solutions restricted adult emergence. There occurred 31 +/- 17.9 % adult emergence from the containers containing 1000 ppm extract solution. From the container containing 125 ppm extract solution, 82.3 +/- 5.6 % adult emerged. The 1000 ppm of extract solution caused 66.2 +/- 19.5 % EI. At 125 ppm extract solution, 12.2 +/- 6.5 % EI was observed. There was a positive correlation between extract concentration and EI % (R square =0.86). The EL50 value of C. nardus was 515.2 ppm. During the study of effect of Cymbopogon nardus whole-plant n-hexane extract on non-target aquatic insects i.e., damselfly and dragonfly nymphs, the extract caused no mortality of any nymph up to 500 ppm. However, at 1000 ppm concentration, the plant extract caused some mortality (5 %). During the study of effect of extract on grass carp fish (Ctenopharingodon idella), there occurred no mortality during 24-hour exposure. During the study of effect of extract on rabbits, there occurred no mortality and found no significant alterations in the normal biochemical and hematological parameters. Photomicrographs of microtome sections of liver and kidney of extract treated rabbit groups showed normal histoarchitecture. From the findings of the present research, it was concluded that the n-hexane extract of C. nardus whole-plant possesses oviposition deterrent and adult emergence inhibition activities against Cx. quinquefasciatus. It was also concluded that the n-hexane extract of C. nardus whole plant is least toxic to damselfly and dragonfly nymphs. The extract does not cause mortality or behavioural abnormality in fish. The ingestion of C. nardus whole-plant n-hexane extract in rabbits do not cause mortality or alterations in the normal biochemical and haematological parameters of rabbits.