Semiochemicals from coccinellid beetles modulate feeding attributes, reproductive parameters and antioxidant enzyme activities in Parthenium beetle, Zygogramma bicolorata Pallister

Abstract

Parthenium is a toxic invasive weed that widely infests agroecosystems worldwide. It hosts both phytophagous chrysomelid beetles used as biocontrol agents and the predaceous coccinellid beetles. This study evaluated reproductive traits, nutrient assimilation and antioxidant enzyme activities of the Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) in the presence of semiochemical tracks left by coccinellid beetles. Results revealed that the presence of coccinellid semiochemical tracks on the weed significantly reduced fecundity and egg viability in Z. bicolorata females. Age-specific fecundity and egg viability followed a triangular pattern, with exposed females reaching peak oviposition and maximum egg viability earlier than unexposed females. Females exposed to semiochemical tracks also showed lower assimilation of triglycerides, glucose and proteins compared to those not exposed. Triglyceride assimilation increased with age, whereas glucose and protein assimilation declined. Activities of superoxide dismutase (SOD) and catalase (CAT) were higher in the absence of semiochemical tracks, while lipid peroxidation (LPO) was elevated in their presence. SOD and CAT activities initially increased with age in both control and experimental setups but declined in older females. In contrast, LPO activity increased initially and then declined with age in the control group but continued to rise with age in the experimental setups. The feeding deterrent effects of semiochemical tracks were species-specific. Overall, these findings indicate that coccinellid semiochemical tracks on Parthenium interfere with the biological control efficacy of Z. bicolorata females.