The analysis of spatial and temporal distribution of Scaphoideus titanus populations is a fundamental tool to effectively control the vector and Flavescence dorée in fragmented viticultural areas

Flavescence dorée (FD) is a yellows disease that causes serious damage in European vineyards. The phytoplasma associated with FD is transmitted mainly by the leafhopper Scaphoideus titanus . Monitoring S. titanus populations is essential for defining the optimal timing of insecticide applications and evaluating the efficacy of control strategies. In the territory of the Consortium Conegliano Valdobbiadene Prosecco Superiore DOCG (northeastern Italy), where severe FD outbreaks were recorded since 2019, S. titanus populations were monitored from 2021 to 2024. During the same years, the spatial and temporal distribution of S. titanus populations was analyzed in four fragmented and critical areas. In 2022, the appearance of first instar nymphs was earlier than in other years, due to higher spring temperatures. Adult population densities have decreased since 2022, due to the effectiveness of pyrethroids used against nymphs. Nymph population densities significantly declined from 2023 onwards. In the four fragmented areas, significant patches and gaps of nymph and adult populations were recorded, with significant aggregations detected in 10 out of 16 analyzed periods in Area 1 and in 8 out of 16 in Area 3. In 2021 and 2022, when chemical control of S. titanus was not really effective, significant associations between nymph and adult spatial distributions were observed in three out of four areas. The distribution of nymphs in early spring, before insecticide application, was significantly associated with that of adults in the late summer of the previous year in three areas in 2022, two areas in 2023 and one area in 2024. In Area 1, nymph and adult patches persisted for two consecutive growing seasons, resulting no longer present only after the application of effective chemical control strategies in all vineyards of this area. For this reason, an area-wide approach to FD management is crucial, as a few infested vineyards can nullify the efforts made in well-managed vineyards.