INFLUENCE OF ABIOTIC FACTORS ON POPULATION DYNAMICS OF LEAF WEBBER DIAPHANIA PULVERULENTALIS AND ITS NATURAL ENEMIES IN MULBERRY

Abstract

ABSTRACT Mulberry the only host plant for rearing silkworms (Bombyx mori) is affected by tukra mealy bug Maconellicoccus hirsutus and leaf webber Diaphania pulverulentalis among many other pests. The incidence of tukra mealy bug M. hirsutus and leaf webber D. pulverulentalis and its natural enemies coccinellids and spiders (Nos./20 plants) were subjected to survery and surveillance for four years. The infestation of tukra mealy bug M. hirsutus and leaf webber D. pulverulentalis was observed through out the year and high (8.18% and 17.13%) in July and November respectively. The population of coccinellids and spiders was high (6.5 and 10.32/20 plants) during November. The infestation of leaf webber (above ETL of 10%) and population of its natural enemies on three varieties (local, MR2 and V1) were correlated with abiotic factors viz., temperature, relative humidity, rainfall and rainy days. Results indicated that the population of parasitoids had significant positive correlation with rainfall. The population of coccinellids, spiders and parasitoids had positive correlation with rainy days and leaf webber infestation. The natural enemies observed in the study were mostly the ladybird predators Chilomenus sexmaculatus and unidentified species of spiders and braconid parasitoids. The braconid parasitoid was marked only in the V1 variety, where leaf webber incidence was higher. Spiders and ladybird were common on both V1 and MR2 varieties during the peak incidence of both tukra mealy bug and leaf webber during October to December.