Differential Compatibility of Essential Oil Nanoemulsions With Aphid Predators: High Selectivity Towards Diptera Syrphidae

ABSTRACT

Nowadays, the control of aphid pests for the defense of commercial crops is crucial, as their demand increases over the years. Since traditional pesticides are widely demonstrated to have critical effects on humans and the environment, great attention should be paid to alternative pest control methodologies. Integrated Pest Management (IPM) allows pests to be managed by combining biological, physical, and chemical methods sustainably, emphasizing biological and low‐impact approaches such as biopesticides and natural predators. In this study, we tested four essential oils (EOs): Laurus nobilis L., Cupressus sempervirens L., Pinus halepensis Mill., and Santolina chamaecyparissus L. against the green peach aphid Myzus persicae (Sulzer, 1776) and three natural enemies available to farmers through biocontrol production facilities: Sphaerophoria rueppellii (Wiedemann, 1830), Adalia bipunctata (Linnaeus, 1758), and Chrysoperla carnea (Stephens, 1836). Mortality rates obtained in toxicity tests performed on Petri dishes highlighted L. nobilis as the most effective EO against the aphid with a recorded mortality of 99% versus control 3.69% at 48 h, while among the predators, the syrphid S. rueppellii proved to be immune to all EOs tested with a recorded mortality of 0% at 48 h for both control and laurel. After identifying the most effective EO and the less susceptible predator, a second assay was carried out on plants. Laurel or pine EO nanoemulsions were sprayed on Capsicum annuum L. leaves of plants infested with aphids and some days after, S. rueppellii larvae were added to test combined effects. The results showed that while EO nanoemulsions alone reduced the aphid population to zero in only a small fraction of plants (15%), this rose to 60% when combined with the predator. Furthermore, our findings suggest the potential to further increase mortality rates by optimizing the timing of predator introduction following the nanoemulsion treatment. These results are promising for identifying optimal timing of product application and predator release in the framework of an IPM strategy.