Patterns of Laboratory Parasitisation Rates of Cotesia flavipes Cameron (Hymenoptera: Braconidae) in Borers of Sugarcane and Sorghum

Abstract

Laboratory parasitisation rates of a native (Indian) and an exotic (Indonesian) population of the gregarious larval endoparasitoid Cotesia flavipes Cameron (Hymenoptera: Braconidae), mass reared by the group-exposure method in glass chimneys, were examined during 1990–1994 on three hosts, namely the sugarcane shoot borer Chilo infuscatellus Snellen, sugarcane internode borer Chilo sacchariphagus indicus (Kapur) and spotted stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). Parasitisation rates of both the Indian and Indonesian populations in individual rearing batches showed considerable variation. Correlation and multiple regression analysis of parasitisation rates in rearing batches and three rearing parameters, viz. percent males, number of larvae and number of larvae per female parasitoid, indicated variable influence of the rearing parameters. Parasitisation rates of the Indian population were positively related to percent males and negatively related to number of larvae and number of larvae per female parasitoid in some hosts. The parasitisation rates of the Indonesian population were negatively related to percent males only in Ch. partellus. Mean monthly parasitisation rates of both populations during the study period fluctuated considerably in different hosts. The role of rearing parameters as well as rearing history of host and parasitoid cultures in parasitisation rates is discussed.