Seasonal incidence and predatory potential of a syrphid fly, Episyrphus balteatus (De-Geer) in relation to Lipaphis erysimi (Kalt.) (Homoptera: Aphididae) on Brassica oleracea var. gongylodes (knol-khol)

摘要

The syrphid fly, Episyrphus balteatus (De-Geer) was found as an important predator of mustard aphid, Lipaphis erysimi (Kalt.) on knol-khol. The seasonal incidence of ;the predator syrphid, Episyrphus balteatus and its prey aphid Lipaphis erysimi werestudied for two consecutive cropping seasons during 2009-2011 in the field. The maximum activity of the predator was recorded in the month of February during both the seasons which was coincided with the maximum abundance of the prey aphid. The numeri-cal density of the predator was recorded tp increase in response to the density of the aphid prey in the field. The feeding potential of the different larval stages were evaluated in the laboratory. The grub of the Episyrphus balteatus was found to consumea total of 411.74±48.16 aphids during its total develop-mental period. The correlation analysis show significant positive correlation between the predator Episyrphus balteatus and prey Lipaphis erysimi. Abiotic factors such as temperature, windspeed and sunshine had also positive correlation with the predator whereas relative humidity and rainfall show negative correlation.