Drought stress and multitrophic interactions: Investigating the effects on aphid performance, plant-mediated changes, and natural enemy dynamics

Research Poster Health & Life Sciences 2025 Graduate Exhibition

Presentation by Bijay Subedi

Exhibition Number 170

Abstract

Climate change is increasing drought frequency, disrupting ecosystem functions and species interactions across trophic levels. These changes affect plant-herbivore dynamics, with cascading effects on predators and parasitoids. This study examines how drought stress influences a tri-trophic system: tomato plants (Solanum lycopersicum), aphids (Macrosiphum euphorbiae), and their natural enemies. We hypothesize that drought stress reduces aphid survival and population growth due to plant trait changes while weakening predator-prey interactions by suppressing herbivore-induced volatile emissions, reducing natural enemy attraction and foraging efficiency. Greenhouse and field experiments compared well-watered and drought-stressed tomato plants. Aphid performance was assessed using survival analysis and population growth models, while predation rates and natural enemy responses were evaluated via field observations and no-choice consumption assays. Drought stress significantly reduced aphid lifespan and population growth, likely due to lower plant quality and increased defenses. Natural enemy abundance was lower on drought-stressed plants, reducing top-down aphid control. Predation rates were higher on well-watered plants in field conditions, but no-choice assays showed predators consumed more aphids from drought-stressed plants, likely compensating for reduced aphid mass and nutritional quality. These findings highlight the cascading effects of drought on multitrophic interactions, emphasizing the importance of both bottom-up (plant-mediated) and top-down (natural enemy-driven) processes in herbivore population dynamics under water-limited conditions. Understanding these interactions is crucial for resilient pest management and conservation strategies amid increasing climate variability.

Importance

This study reveals how drought, intensified by climate change, disrupts natural pest control in agriculture. Drought stress weakens plants, reducing their quality for aphids while also making them less attractive to natural predators. As a result, aphid populations decline, but their natural enemies become less effective, weakening biological pest control. Although predators consume more aphids on drought-stressed plants in no-choice feeding assays, they are less likely to visit drought-stressed plants in natural field environments where they have a choice. These findings highlight how climate change alters food webs, potentially increasing pest problems. Understanding these interactions is crucial for developing resilient pest management strategies and protecting crops under increasing drought conditions, helping farmers adapt to a changing climate.

DEI Statement

Tomato production is a key livelihood for small, family-owned farms and historically underserved growers, including non-white and female farmers, who face systemic barriers to resources. Water scarcity disproportionately affects these farmers, reducing yields and increasing pest risks. This research examines how drought disrupts natural pest control, a vital, cost-effective strategy for sustainable farming. By addressing the intersection of climate resilience, pest management, and economic stability, this work supports equitable access to sustainable agriculture solutions. Findings will inform policies and practices that enhance the resilience of marginalized farming communities, ensuring they can adapt to climate challenges while maintaining productivity and livelihoods. This research directly contributes to agricultural equity by empowering diverse growers with science-driven, inclusive pest management strategies.