Aphid honeydew in intraguild interactions: enhancing predator mobility, foraging, and dynamics between Adalia bipunctata and Episyrphus balteatus

Honeydew is a nutrient rich excretion of aphids. This substance also emits kairomones, serving as a signal that attracts aphid predators and thereby influences the interaction among plants, aphids, and other predators. The overall aim of this study was to investigate the role of honeydew from two aphids species, Aphis fabae Scopoli, 1763 and Acyrthosiphon pisum (Harris 1776) in the predatory behavior of Adalia bipunctata (Linnaeus 1758) and Episyrphus balteatus (De Geer 1776). Specifically, we aimed to (1) evaluate the impact of honeydew on A. bipunctata and (2) E. balteatus and on intraguild interactions (IGI) among them. Our results showed that the presence of honeydew enhanced the mobility of predators by stimulating foraging behavior. In addition, the number of aphids consumed was significantly higher in the presence of honeydew. Interestingly, the predators were more attracted to A. fabae in the presence of A. pisum honeydew. These findings highlight the key role of honeydew in intraguild relationships, altering the prey’s perception from being less preferred to becoming more appealing to predators, akin to their favored prey. These results provide interesting perspectives to improve aphid biological control.