# Phytochemical-Mediated Tritrophic Interactions: Effects of Pepper and Eggplant Cultivars on the Green Peach Aphid Myzus persicae (Sulzer) and Its Predators

## TL;DR

This study shows that the eggplant cultivar 'Longo' affects aphids negatively and benefits their predators, due to its high levels of plant chemicals.

## Contribution

The study demonstrates how plant chemistry can influence tritrophic interactions by affecting both herbivores and their predators.

## Key findings

- The eggplant cultivar 'Longo' had the highest levels of secondary metabolites and defensive enzymes.
- Aphids on 'Longo' had a lower intrinsic rate of increase compared to other cultivars.
- Predators fed aphids from 'Longo' showed higher population growth and offspring production.

## Abstract

Plants exhibit various chemical traits that influence their interactions with herbivores and higher trophic levels. In this experiment, we investigated the effects of different host plant cultivars on the life history traits of the green peach aphid and its predators, Aphidoletes aphidimyza and Chrysoperla carnea. Phytochemical analyses revealed that the eggplant cultivar ‘Longo’ contained the highest concentrations of secondary metabolites and key defensive enzymes. The intrinsic rate of increase (r) was lowest for aphids on ‘Longo’, but significantly higher for both predator species when fed aphids from this cultivar. These findings suggest that elevated secondary metabolite levels on ‘Longo’ negatively impact Myzus persicae performance while benefiting its predators, highlighting the role of host plant chemistry in shaping tritrophic interactions.

The diverse phytochemical profiles of host plants can significantly influence their interactions with herbivores and natural enemies. This study investigated the ‘bottom-up’ effects of several bell pepper and eggplant cultivars on the development, reproduction, and survival of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), and its predators, Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae). We analyzed the leaves of each cultivar for levels of total flavonoids, phenols, anthocyanins, and key defensive enzymes. The eggplant cultivar ‘Longo’ exhibited the highest concentration of secondary metabolites. Aphid populations reared on this cultivar’s leaves showed a slower growth rate compared to those on other cultivars. Conversely, predators fed on these aphids demonstrated higher rates of population growth and produced more offspring. Accordingly, the intrinsic rate of natural increase (r) was lower for aphids feeding on ‘Longo’, but significantly higher for both A. aphidimyza and C. carnea when fed those aphids. These results demonstrate that elevated secondary metabolites on ‘Longo’ suppress the performance of M. persicae while enhancing predator efficiency, thereby providing a phytochemical-based approach that can serve as an effective component of integrated pest management (IPM) programs.