Efficacy of Beauveria bassiana strain ATCC 74040 (Naturalis®) against the leafhopper Scaphoideus titanus Ball under open-field conditions

Abstract: The leafhopper, Scaphoideus titanus Ball (Cicadellidae), native to North America, was introduced accidentally to Europe, where it has become a key pest by acting as the principal vector of the grapevine flavescence dorée phytoplasma (FD). FD is a quarantine disease (EPPO A2 List), and insecticide sprays against its vector are mandatory in several European countries. Due to the prolonged egg-hatching period of the target pest, repeated sprays may be necessary to effectively control the pest. The most effective insecticides against S. titanus allowed in organic viticulture, are products based on pyrethrins. Due to their low persistence and their toxicity to non-target organisms, research on alternative control tools and measures, to be included in organic and sustainable plant protection strategies, is ongoing. The aim of these studies was to investigate the efficacy against S. titanus of the microbial pest control agent Beauveria bassiana strain ATCC 74040 (formulated product: Naturalis®), applied twice by itself, in comparison to organic and chemical reference insecticides under open-field conditions. The microbial control agent did not provide complete pest control, but reached final efficacy values in reducing the number of live S. titanus ranging from 69 up to 83%. Perspectives and options for the inclusion of B. bassiana strain ATCC 74040 in S. titanus control strategies are discussed.