Studies on insect-pests of castor in the agro-ecosystem of Manipur.
A field study was conducted on the incidence of insect pests on 2 cultivars of castor (Ricinus communis), namely 48-1 and Red petiole (local), for 3 consecutive years (2001-03) under rainfed condition in Manipur, India. More than 20 species of insect pests were found associated with castor, but many of them were highly irregular in occurrence over years, distributed in patches with low population causing no remarkable damage to the crop. Only 10 species belonging to Lepidoptera, Hemiptera, Orthoptera and Thysanoptera showed variable economic importance and of them, 5 species were found regular with high degree of severity (moderate to serious) as major pests. Most of the insect pests were either defoliators or sucking pests. Moreover, few insects, i.e. Empoasca flavescens [E. vitis], Trialeurodes ricini, Retithrips syriacus and Amsacta moorei, had achieved the pest status in the state in recent years.