<i>Brassica rapa</i> treatments with methyl salicylate enhance foraging capacity of generalist natural enemies in a concentration-dependent manner

The aphid Myzus persicae Sulzer (Hemiptera: Aphididae) causes significant crop damage by feeding on plant tissues, transmitting viruses, and reducing agricultural productivity. Challenges associated with chemical control methods, such as the development of pest resistance and adverse environmental impacts, highlight the need to enhance the efficacy of natural enemies for sustainable pest management. Methyl salicylate (MeSA) has been extensively studied in pest management using baited traps and slow-release packets; however, its role in enhancing natural enemy behavior through induced plant defenses remains underexplored. This study examines the effect of MeSA applied to Brassica rapa (Brassicales: Brassicaceae) on the behavior and performance of 2 key biocontrol agents, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and Aphidius gifuensis Ashmead (Hymenoptera: Braconidae). We hypothesized that MeSA enhances the attraction of natural enemies in a concentration-dependent manner. To test this, 4 MeSA concentrations (25, 50, 75, and 100 mg/L) were applied, with control plants treated using deionized water. Bioassays were then conducted to evaluate predator preferences, parasitism rates, foraging behavior, and behavioral responses in the olfactometer. Results showed that MeSA-treated plants significantly attract natural enemies, with pronounced effects at higher concentrations. Specifically, MeSA increased parasitism rates, improved predator foraging efficiency, and heightened predator preference for treated plants. This study demonstrates the potential of MeSA in enhancing biological control strategies against M. persicae by improving the efficacy of natural enemies. The findings highlight the potential of applying MeSA treatment to enhance the recruitment of biological control agents by inducing plant defenses, offering a sustainable approach to reducing aphid infestations in pest management programs.