Metabolic trade-offs in sugar beet under drought and beet leaf miner infestation: implications for herbivore success.

Increasing frequency of drought under climate change threatens crop production and intensifies pest pressures, yet the interactive effects of drought and herbivory on plant metabolism and ecological outcomes remain incompletely understood. We subjected sugar beet (Beta vulgaris) plants to moderate and high drought, alone or with infestation by the beet leaf miner (Pegomya cunicularia), and analyzed plant physiology, central metabolites, and volatile organic compound (VOC) emissions. Drought alone reduced growth and photosynthetic efficiency, while combined stress led to accentuated metabolic reprogramming, including increased amino acids and organic acids, and a concurrent suppression and alteration of VOC emissions, especially in plants affected by high drought and leaf mining. The resulting changes in VOC blends reduced plant attractiveness to ovipositing females, leading to fewer eggs laid on severely stressed plants. In contrast, moderate drought generated a nutrient-rich environment: larvae feeding on these plants exhibited the highest growth rates, larger pupae and adults, and increased feeding damage. High drought strongly limited both plant water content and larval development. These findings reveal a stress-dependent trade-off between enhanced leaf nutritional quality and reduced host detectability, underscoring the importance of integrating multi-stress plant biology for future pest management and crop resilience.