Oviposition-Site Selection and Egg-Hatching of <em>Aedes aegypti</em> and <em>Aedes albopictus </em>(Diptera: Culicidae) in Leaf Infusions of Three Invasive Plants Found in Sri Lanka

Abstract

Aedes aegypti and Aedes albopictus (Diptera: Culicidae) are the main human arboviral vectors in Sri Lanka. The oviposition behaviour of Aedes mosquitoes determines their survival and population dispersion. Using varying concentrations of plant leaf infusions is a vital technique in determining mosquito oviposition behaviour. The objective of this study was to evaluate the oviposition behavior and egg-hatching rate of Ae. aegypti and Ae. albopictus to three leaf infusions of three invasive plants found in Sri Lanka. The oviposition media were prepared using guinea grass (Megathyrsus maximus), alligator weed (Alternanthera philoxeroides) and Austroeupatorium (Austroeupatorium inulifolium). Each oviposition medium was prepared in four different concentrations: 25%, 50%, 75%, and 100%. The ovitraps were placed in a rubber plantation in Rathnapura district, Palmadulla, Sri Lanka in order to determine the oviposition site selection towards those leaf infusions. Different plant infusions have a significant effect on the oviposition and egg hatch rate of Ae. aegypti and Ae. albopictus. Accordingly, the highest number of eggs has been laid in ovitraps with a 25% concentration of M. maximus infusion. The ovitrap positivity index values were highest in A. philoxeroides at 25%, 50% and 75% concentrations; M. maximus at 25%, 50% and 100% concentrations; and A. inulifolium at 25% and 75% concentrations. Despite the type of infusion and concentration, the egg-hatching rate was highest on the second day of rearing. Ae. aegypti and Ae. albopictus responded differently to different plant infusions based on the plant species and biomass employed. The study shows that organic matter infusions composed of guinea grass improve trap effectiveness and attract females more effectively than ovitraps using aerated tap water. The use of leaf infusions of guinea grass at 25% concentration as an attractant in combination with lethal substances to control container-breeding mosquito species is suggested as a strategy in integrated pest management.