Compensatory feeding by lady beetles: enhanced biocontrol potential of Harmonia axyridis against caterpillars in salinity-affected agro-ecosystems

Abstract The increasing salinization of agricultural land is a pressing problem, altering how plants interact with organisms across multiple trophic levels. While salinity-induced changes in plant chemistry are known to affect insect herbivores, it remains unclear how these changes shape predator responses. Here, we examined how prey quality (tomato fruitworm caterpillars— Helicoverpa zea ), shaped by soil salinity influences the foraging and consumptive behavior of the generalist predatory Asian lady beetle ( Harmonia axyridis ). We tested how salt stress in host plants (tomato – Solanum lycopersicum ) and "salty" H. zea caterpillars as prey shape predator attraction, feeding dynamics, and survival. Caterpillars reared on salt-treated artificial diets showed reduced protein content and slower growth. Despite this potentially lower prey quality, H. axyridis consumed more of the “salty” prey than the “non-salty” prey, suggesting a compensatory feeding response. Petri dish dual-choice assays showed no consistent preference for prey type during initial behavioral stages (touch, bite, consumption), but total intake was significantly higher for the “salty” caterpillars. In Y-tube olfactometer choice assays, predators were equally attracted to non salt-stressed and salt-stressed plants, indicating that salinity did not disrupt olfactory cue-mediated predator recruitment. Together, these results suggest that H. axyridis may adjust its feeding behavior to compensate for likely reduced prey quality and enhance biocontrol potential in salinity-affected systems.