Insecticidal Effect of Entomopathogenic Nematodes and the Cell-Free Supernatant from Their Symbiotic Bacteria against (Hemiptera: Aphrophoridae) Nymphs.

The meadow spittlebug (Hemiptera: Aphrophoridae) is the primary vector of (Proteobacteria: Xanthomonadaceae) in Europe, a pest-disease complex of economically relevant crops such as olives, almonds, and grapevine, managed mainly through the use of broad-spectrum pesticides. Providing environmentally sound alternatives to reduce the reliance on chemical control is a primary challenge in the control of and, hence, in the protection of crops against the expansion of its associated bacterial pathogen. Entomopathogenic nematodes (EPNs) are well-known biocontrol agents of soil-dwelling arthropods. Recent technological advances in field applications, including improvements in obtaining cell-free supernatant from their symbiotic bacteria, allow their successful implementation against aerial pests. Thus, this study aimed to evaluate, for the first time, the efficacy of EPN applications against nymphal instars of We tested four EPN species and the cell-free supernatant of their corresponding symbiotic bacteria: -, -, -, and - subsp. . First, we showed that 24 and 72 h exposure to the foam produced by nymphs did not affect virulence. The direct application of steinernematid EPNs provided promising results, reaching 90, 78, and 53% nymphal mortality rates after five days of exposure for , , and , respectively. Conversely, the application of the cell-free supernatant from resulted in nymphal mortalities of 64%, significantly higher than observed for species after five days of exposure. Overall, we demonstrated the great potential of the application of specific EPNs and cell-free supernatant of their symbiont bacteria against , introducing new opportunities to develop them as biopesticides for integrated management practices or organic vineyard production.