The impact of salinity stress on plant-insect interactions

The progressive salinization of agricultural land poses a significant threat to global crop productivity. Concurrently, the presence of insect herbivores adds additional pressures, compounding agricultural losses. Despite extensive research on the impact of salinity on plant physiology, very few studies try to understand its implications for plant-insect interactions. In this study, we show that salt-stressed tomato plants (Solanum lycopersicum cv. Better Boy) are poor hosts for the corn earworm (Helicoverpa zea), reducing caterpillar preference and performance. We shed light on the effect of ionic toxicity on insect behavior and growth, an often-overlooked aspect. Furthermore, we explore the cascading impacts of salinity stress on higher trophic levels, such as on the predatory Asian lady beetle (Harmonia axyridis) and the parasitoid wasp Microplitis croceipes. We investigate how insect quality as prey (for predators) or hosts (for parasitoids) changes with plants under salt stress. Additionally, we study indirect plant defenses under salt stress by using volatile organic compound (VOC) analysis and investigate natural enemy recruitment via Y-tube olfactometer assays. Intriguingly, we find that predators prefer to feed on non-salty caterpiilars, they are attracted to salt-stressed plants. Parasitoid performance parameters are negatively influenced by salt, however, they are attracted to plants without salt stress. We show how the effects of salt-stress influence plant-insect interactions, impacting plants, their insect herbivores, and their natural enemies.