Host Plant-mediated Tritrophic Interactions among Castor Genotypes, Conogethes punctiferalis (Guenee) and Its Larval Parasitoid Eriborus trochanteratus (Morley)

Abstract

Background: Host plant-mediated tritrophic interactions can influence both pest performance and the effectiveness of natural enemies in integrated pest management. Aims: This study investigated interactions among castor (Ricinus communis L.) genotypes, the shoot and capsule borer Conogethes punctiferalis (Guenée), and its larval parasitoid Eriborus trochanteratus (Morley), with emphasis on parasitisation, parasitoid development and associations with biochemical constituents. Study Design: Field, laboratory and insect-proof glasshouse experiments were conducted using a Randomised Block Design (RBD) and Completely Randomised Design (CRD), as appropriate for each experiment. Place and Duration of Study: ICAR–Indian Institute of Oilseeds Research (IIOR), Hyderabad, Telangana, India, during 2023–2025. Methodology: Seventy-five castor genotypes were evaluated under field conditions for natural parasitisation of C. punctiferalis by E. trochanteratus. Based on field response, twenty-two representative genotypes were selected for laboratory and glasshouse studies, while the developmental biology of E. trochanteratus was assessed on eight representative genotypes. Biochemical constituents of capsule and seed tissues were estimated and correlated with parasitoid parasitisation using Pearson's correlation analysis. Results: Significant variation in parasitisation was observed among the castor genotypes under field, laboratory and glasshouse conditions. Field parasitisation ranged from 4.38 to 29.58 %, with the highest values recorded on RG-3141 and the susceptible check DCS-9 (29.58%) and the lowest on ICS-121 (4.38%). Under laboratory and glasshouse conditions, parasitisation ranged from 18.33 to 35.00 % and 15.00 to 30.00%, with the highest values recorded on GCH-6 (35.00%) and Geetha (30.00%), respectively. The total developmental period and adult longevity of E. trochanteratus ranged from 10.17 to 13.67 days and 5.83 to 7.50 days, respectively. Pearson's correlation analysis revealed significant negative associations between per cent parasitisation and total free amino acid content in capsule (r = −0.496) and seed (r = −0.479), while other biochemical constituents showed non-significant correlations. Conclusion: Host plant genotype significantly influenced the tritrophic interactions among castor, C. punctiferalis and E. trochanteratus by affecting parasitoid parasitisation and developmental performance. The significant association between total free amino acids and parasitoid parasitisation highlights the role of host plant biochemical constituents in mediating these interactions. The findings provide useful information for integrating host plant resistance with biological control for the sustainable management of C. punctiferalis in castor.