Distribution, host range and bionomics of rhopalosiphum nymphaeae (Linnaeus, 1761), a polyphagous aphid in aquatic vegetables

Abstract

The present study records the occurrence of water lily aphid, Rhopalosiphum nymphaeae (Linn, 1971) on different aquatic plants from Varanasi and adjoining regions, Uttar Pradesh, India for the first time. Both nymphs and adults prefer to feed on petiole, leaf lamina and buds towards terminal portion of different aquatic plants. They suck the cell sap resulting in curling of leaves, stunted plant growth with lower number of fruits in water chestnut. Further, the honey dew deposited on the leaves favours the development of black sooty-mould and hinders the normal photosynthetic activity of the plants. Infestation of aphid started in the region on water chestnut during last week of October (1.35 aphids leaf-1) coinciding with the initiation of winter in the region and gradually increased with highest peak (21.95 aphids leaf-1) during fourth week of January. Amongst the different aquatic host plants under study in the region, olfactometer study showed significantly highest number of R. nymphaeae (28%) attraction towards lotus followed by of water chestnut (21.3%) and water lily (20%) and the least was with water hyacinth (4%). Amongst the biopesticides tested, L. lecanii @ 5 g lit-1was found most promising with lowest median lethal time (31.09 h) followed by neem oil (1%) (41.59 h) and M. anisopliae (43.95 h).