Direct and indirect effects of two endophytic entomopathogenic fungi on survival and feeding behaviour of meadow spittlebug Philaenus spumarius

Beyond Xylella, Integrated Management Strategies for Mitigating Xylella fastidiosa Impact in Europe (BeXyl) (Grant Agreement 101060593). Partner/Coordinador principal: Blanca B. Landa del Castillo, Investigadora Científica del Instituto de Agricultura Sostenible (IAS-CSIC).The most effective way to contain spread of the plant pathogen Xylella fastidiosa in Europe is to manage populations of its main insect vector, Philaenus spumarius L. (Hemiptera: Aphrophoridae). The action of some entomopathogenic endophytic fungi (EEF) on insect pests, directly through contact or indirectly by internal colonization of host plant tissues, may offer an excellent control option within integrated pest management (IPM) programmes. This study evaluated the impact of two EEF strains as control agents of P. spumarius (Metarhizium brunneum strain EAMa 01/58-Su and Beauveria bassiana strain EABb 01/33-Su [Hypocreales: Clavicipitaceae and Cordycipitaceae, respectively]); both strains were known to be excellent control agents of many other serious chewing and sap-sucking agricultural pests. First, the pathogenicity of strains applied directly to P. spumarius adults was evaluated, resulting in 50.0% and 32.0% mortality and a mean survival time of 4.7 and 6.2 days for M. brunneum and B. bassiana, respectively. Furthermore, colonization of Sonchus oleraceus by EEFs was observed after both soil and foliar applications. Greatest colonization (91.0%) was observed in plants treated with foliar applications of M. brunneum. Based on these results, we evaluated the feeding behaviour of P. spumarius on S. oleraceus plants previously colonized by M. brunneum using the ‘Electrical Penetration Graph’ technique. P. spumarius fed in a similar way on EEF-colonized and non-colonized S. oleraceus plants, with the exception that insects feeding on colonized plants reached xylem vessels faster than insects feeding on non-colonized plants. In addition, significantly higher mortality of P. spumarius was observed when feeding on plants treated by M. brunneum compared with the control. The duration of xylem ingestion events indicates that P. spumarius preferred to feed on basal leaves of the plant compared with apical leaves. Our results indicate strong potential for strain EAMa 01/58-Su of M. brunneum to be used as part of an X. fastidiosa IPM programme.This present study was supported by: grant PID2019-103844RB-I00 from the Spanish Ministry of Science and Innovation, Spain; by the Project BeXyl (Beyond Xylella, Integrated Management Strategies for Mitigating Xylella fastidiosa impact in Europe - Grant ID No 101060593) from the European Union’s Horizon Action ‘Food, Bioeconomy Natural Resources, Agriculture and Environment’ Programme; and by grant FP19-XYLELLA from IMIDRA. Also, this publication is part of the project TED2021-132458B-100, funded by MCIN/AEI/10.13039/501100011033 and by the European Union "NextGenerationEU"/PRTR. Recovery, Transformation, and Resilience Plan - Funded by the European Union - NextGenerationEU. Also, we acknowledge financial support from the Spanish Ministry of Science and Innovation; and the Spanish State Research Agency, through the Severo Ochoa and María de Maeztu Program for Centers and Units of Excellence in R&D (Ref. CEX2019-000968-M).With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2019-000968-M).Peer reviewe