Abstract

                                Considerable progress has been made in the recent past in the study of insect resistance in crop plants, and varieties resistant to pests have been evolved. Castor is subjected to the severe attack by many insect pests particularly the semilooper, Achoea janata L., and the shoot and capsule borer, Dichocrocis punctiferalis Guen. year after year in several parts of the country. Even though effective chemical method of control is available against many of these pests, the importance of evolution of pest-resistant varieties is increasingly felt in recent years. Castor has been studied by different authors for its resistance to many pests. Detailed investigations in screening large number of castor varieties for resistance to the jassid Empoasca flavescens (F) were undertaken by Jayaraj (1966-a, 1967-a). Preliminary observations were made on their resistance to the shoot and capsule borer Dichocrosis punctiferalis Guen. (Basu 1947, David et al 1964, Sulochanabai et al 1968), the European corn borer Ostrinia nubilalis (Hubn.) (Kittock and Williams 1963), the whitefly Trialeurodes ricini Misra (David and Radha 1964), and the red spider mite Tetranychus telarius (L) (Chandrasekharan et al 1964). The information available on castor resistance to the caterpillar pests, particularly the foliage feeders, is very meagre and hence detailed screening of several varieties for resistance to nine leaf-eating caterpillar pests and the shoot and capsule borer was undertaken in two seasons (1962-1964) and the results are presented in this paper. Attempts have been made to understand the possible mechanism of resistance in the case of two major pests viz., A. janata and D. punctiferalis and also to understand the effect of food plant of A. janata on the braconid parasite Microplitis ophiusae R.

Key words :