Impact of intercropping on predators of insect pests of pigeonpea in rainy and post rainy season.

Abstract

Castor (Ricinus communis L.) (Malpighiales: Euphorbiaceae) is an important non—edible oilseed cash crop grown across many parts of arid and semi—arid regions in India. Castor is grown for its beans, which yield non—edible oil mainly used in the manufacturing of paints, lubricants, soaps, hydraulic brake fluids, polymers, and perfumery products, among others; there are several derivatives of castor oil that are used in a variety of industries. Fluctuations in productivity levels of castor are experienced for two main reasons: first, it is grown as a rain—fed crop, and as a long—duration crop is subject to the vagaries of the monsoon; second, it attracts a large number of pests including the semilooper, Achaea janata L. (Noctuidae: Lepidoptera), and the shoot and capsule borer, Conogethes punctiferalis Guenee (Crambidae: Lepidoptera). Achaea janata and C. punctiferalis occur during early and late stages of crop growth, respectively (Singh 1987). Incidence of A. janata is generally noticed from vegetative to early reproductive phase of the crop (Tahiliani 1985; Basappa and Lingappa 2001). A peak level of infestation of A. janata causes excessive defoliation affecting photosynthesis. Later, the larvae eat away the tender capsules of primary and secondary spikes. It is estimated that castor yields are reduced by 30–50% due to A. janata alone. Incidence of C. punctiferalis is commonly noticed in the later stage of crop growth, especially secondary and tertiary spike orders. Larvae web the tender capsules, bore into them, and eat away the kernel. The borer attacks various plant parts such as the shoots, inflorescences, and capsules, causing considerable yield losses (Singh et al. 1992).