ABSTRACT
Present investigations evaluated the impact of Argemone mexicana stem extracts on the reproductive fitness of dengue vector, Aedes aegypti, assessed in terms of oviposition deterrent and ovicidal potential. The oviposition deterrent studies of the extracts, prepared using petroleum ether, hexane, benzene, acetone, and ethanol as the solvents, revealed the maximum deterrence potency of the petroleum ether extracts with a significant 15.6% ED at 60 ppm rising by 83.8% at 1000 ppm to 99.4% effective deterrence (ED). Other stem extracts were found to be ineffective at 60 ppm, though resulted in 85.3-96.2% ED and diminished fecundity in A. aegypti at 1000 ppm. Further, A. mexicana stem extracts exhibited moderate ovicidal potential against A. aegypti eggs causing only 42.65-67.85% egg mortality at 1000 ppm, the lowest hatch of 32.15% caused by the benzene extract. Other stem extracts also failed to express effective ovicidal potency with the percent egg hatch ranging between 96.6 and 99.0 at 400 ppm, and 78.8 and 99.0 at 600 ppm. Our results suggest the significant but variable efficacy of A. mexicana stem extracts causing reproductive disadvantage in A. aegypti.
ABSTRACT
The larvicidal, behavioral, and morphological response of dengue vector, Aedes aegypti treated with deleterious weed, Argemone mexicana, was explored. The 1,000 ppm extracts of A. mexicana leaf, stem, and roots prepared in five different solvents (petroleum ether, hexane, benzene, acetone, and ethanol) were screened for their larvicidal activity against dengue vector establishing the efficacy of petroleum ether and hexane extracts. Other extracts, unable to give 100% mortality, were considered ineffective and discarded from further study. Larvicidal bioassay conducted with selected extracts confirmed the higher efficacy of hexane extracts exhibiting 1.1- to 1.8-fold more potential than the petroleum ether extracts. The results further revealed 1.6- to 2.4-fold higher efficacy of root extracts than those prepared from the leaves and stem of A. mexicana. The hexane root extract of A. mexicana was found to be the most effective larvicide with LC50 value of 91.331 ppm after 24 h of exposure causing 1.8 and 2.4 fold more toxicity as compared to the hexane leaf and stem extracts, respectively. Prolonged exposure of the larvae to the extracts resulted in increased toxicity potential of the extracts. Observations of the treated larvae revealed excitation, violent vertical, and horizontal movements with aggressive anal biting behavior suggesting effect of extracts on their neuromuscular system. Morphological studies of the treated larvae revealed the demelanization of cuticle and shrinkage of internal cuticle of anal papillae indicating the anal papillae as the probable action sites of the A. mexicana extracts. The potential of A. mexicana as new larvicides against dengue vector are being explored.