Assessment of Insect Pest Dynamics and Avoidable Yield Loss in Castor Hybrids under Protected and Unprotected Conditions in Tamil Nadu, India

Field experiments were conducted during Kharif seasons of 2012, 2013 and 2014 to assess the incidence of major insect pests and quantify avoidable yield losses in castor (Ricinus communis L.) hybrids under protected and unprotected cultivation. Three hybrids viz., DCH 177, 48-1 and DCH 519 were evaluated at the Tapioca and Castor Research Station, Yethapur, in replicated plots. The results revealed that semilooper (Achaea janata), Spodoptera litura, hairy caterpillar (Euproctis fraterna), capsule borer (Conogethes punctiferalis), leafhopper (Empoasca flavescens) and thrips (Retithrips syriacus) were the predominant insect pests. Mean pest incidence was consistently higher in unprotected plots, with semilooper and Spodoptera populations ranging from 2.87–3.80 and 2.00–2.70 larvae per plant, respectively, compared to 1.43–1.63 and 0.53–0.70 larvae per plant in protected treatments. Capsule borer damage reached a maximum of 7.15% in unprotected DCH 519. Leafhopper and thrips counts were significantly higher under unprotected conditions. Protected treatments maintained higher seed yields (1355–2280 kg ha⁻¹), with avoidable yield losses ranging between 30–34%. Among hybrids, DCH 48-1 recorded the highest yield loss, whereas DCH 519 exhibited greater resilience. The findings underscore the critical role of integrated pest management in sustaining productivity and profitability in castor cultivation.