Effect of Host Density and Host-Parasitoid Ratio on Parasitization of Pyrilla perpusilla (Walker) by Epiricania melanoleuca (Fletcher)

Abstract

Laboratory and field studies were carried out on the influence of host-parasitoid ratio on parasitism of Pyrilla perpusilla (Walker) (Homoptera: Lophopidae) by Epiricania melanoleuca (Fletcher) (Lepidoptera: Epipyropidae). Enhanced parasitism was observed with increased host-parasitoid ratio from 48.1 per cent at 1: 1 to 84.9% at 1: 4 ratios. Enhanced pupation was also observed with increase in the host-parasitoid ratio (46.1 to 79.6%). The host-parasitoid ratio of 1: 4 at 5 pyrilla per leaf was found optimum for mass multiplication of E. melanoleuca in laboratory conditions. Under field condition non-significant effect of life stages (nymphs 80.0 and adults 77.8%) of pyrilla was noticed on their parasitization by E. melanoleuca. In field conditions also, enhanced parasitization was noticed with increase in host-parasitoid ratios from 1: 1 to 1: 7, but 1: 3-1: 5 ratio at a host density of 5 pyrilla per leaf resulted in better increase in field parasitism.