Light and sem studies on the life stages of illeis indica (TIMB.) and its predatism on phyllactinia corylea (PERS.) karst. infecting mulberry

Abstract

The fungivonis insect Illeis indica is a potential biocontrol agent of Phyllactinia corylea which causes powdery mildew in mulberry. The present study by light and scanning electron microscopy explains the life stages of I. indica and its feeding behaviour on P. corylea borne on infected mulberry leaves. The eggs are laid in clusters of 5–23 on the abaxial surface of infected leaves. Each egg has 16–18 aeropyles circularly arranged at its distal end around a micropylar plate. Total larval period of I. indica is about 15.60 days with four instars and its life cycle is completed in 38.50 days. The grubs feed only on conidia during first instar, on conidia and conidiophores during second instar, and also on parts of mycelia during third instar. The final instar grubs feed on entire aerial mycelial mass leaving only stomatopodia and hyphal remnants attached to them. Pupation is for 6–7 days and the pupae remain motionless and attached to the abaxial leaf surface. Adults also feed voraciously on the fungal mass and the fertilized females lay eggs after about 7.03 ±0.144 days. The grubs and adults clear off the fungal mass from the infected leaves without leaving any mycelial patch and the fungus does not regenerate on such cleared leaves. Field observations indicated a drastic fall in the incidence of powdery mildew disease in mulberry even in the usual peak disease period, with the increased population of I. indica in the mulberry garden.