Spodoptera frugiperda larvae fed with different host plants influence the demography, biocontrol effectiveness and functional response of the parasitoid, Bracon brevicornis

Spodoptera frugiperda (FAW) is a globally invasive pest inflicting significant crop losses. The idiobiont parasitoid Bracon brevicornis offers sustainable control, but host plant-mediated effects on its fitness, parasitism and functional response remain poorly understood. We evaluated the developmental traits, reproductive fitness, parasitism efficiency, and functional response of B. brevicornis using FAW larvae reared on maize and castor. Parasitoids developing on maize-fed FAW completed immature development faster and exhibited greater adult longevity (25.80 ± 0.31 d) and fecundity (281.77 ± 1.69 eggs) than those from castor-fed FAW (longevity: 23.03 ± 0.28 d and fecundity: 244.74 ± 0.49 eggs). Parasitoid population parameters, including intrinsic rate of increase (r = 0.226 ± 0.01 d⁻¹) and finite rate of increase (λ = 1.254 ± 0.013 d⁻¹), were significantly higher on maize fed FAW in contrast to castor fed FAW (r = 0.176 ± 0.01 d⁻¹ and λ = 1.192 ± 0.012 d⁻¹). Total effective parasitism, non-effective parasitism, and killing rate were also higher for parasitoids which developed using maize-fed FAW (47.076 ± 0.478, 43.230 ± 0.327, and 90.230 ± 0.470 larvae/female, respectively). Greenhouse experiments revealed higher effective parasitism (37%) and killing rates (77%) for parasitoids which developed on maize fed FAW as compared to castor fed FAW. Functional response analysis revealed a Type II response of parasitoids parasitizing both maize or castor-fed FAW, with higher searching efficiency and shorter handling time on maize. Overall, host plant quality strongly influences parasitoid fitness and biocontrol efficiency, underscoring the importance of plant-mediated effects in integrated pest management strategies.