Oviposition selection, prey preference, and release strategies enhance the synergistic control of Myzus persicae by Aphidoletes aphidimyza and Aphidius gifuensis

BACKGROUND: The parasitoid Aphidius gifuensis and predator Aphidoletes aphidimyza are widely used in the inundative biological control of Myzus persicae. However, whether intraguild predation (IGP) between these two natural enemies undermines or enhances pest suppression when they are released simultaneously remains unclear. Here, we conducted oviposition site selection and prey preference assays to assess their behavioral responses to IGP risk and conducted glasshouse cage experiments to evaluate the efficacy of different release strategies (single, simultaneous, and sequential releases with an 8-day interval) for aphid control. RESULTS: Aphidoletes aphidimyza females laid significantly more eggs on plants bearing unparasitized aphids (33.9) than on those with 3- or 6-day-old parasitized aphids (21.3 and 7.9, respectively) and avoided plants with mummies. All larval instars of Aphidoletes aphidimyza preferred first-instar over third-instar aphids (Manly's β > 0.5), and second and third instars preferred unparasitized over parasitized prey (β = 0.78, 0.72, respectively). Aphidius gifuensis also preferred first-instar aphids (β = 0.63), this preference was intensified in the presence of adult predators (β = 0.74). In glasshouse trials, releasing Aphidoletes aphidimyza 8 days before Aphidius gifuensis (FAAG) achieved the highest percentage reduction in Myzus persicae (89.1%), significantly outperforming Aphidius gifuensis (17.5%), Aphidoletes aphidimyza (79.1%) alone, and the reverse release order (66.7%). CONCLUSION: The combination of Aphidius gifuensis and Aphidoletes aphidimyza synergistically suppressed Myzus persicae. Their different prey-stage preferences reduce IGP, and the release of predators first yields the best control effect. This will help optimize field release strategies for these two natural enemies.