Population ecology of Empoasca vitis (Göthe) and Scaphoideus titanus (Ball) in Bordeaux vineyards: Influence of migration and landscape

Adult and nymphal population dynamics of two vine pests, the leafhoppers Empoasca vitis and Scaphoideus titanus, were monitored over a 4-year period on five plots. Two E. vitis nymphal population peaks were situated between three adult flight peaks. Overwintering adults migrated from overwintering to intermediate host plants before vine bud burst, and then to vineyards. Correlations between these immigrants and end of season emigrants confirm that adults overwinter locally. Adult populations were related, in magnitude and physiological time (day-degrees), to the subsequent nymphs, not to the preceding ones. The summer adult generation varied little over years and occurred simultaneously in all plots, suggesting massive migrations. The damage-causing summer nymphal populations varied both over years and over plots. Nymphal counts should start 250 day-degrees (base 7.4 °C) after the summer adult peak, on plots presenting the highest number of adult trappings. S. titanus showed a high year-to-year variability in the adult stage and a high variability over plots in the nymphal stage. No clear explanation could be found in examining environment, plot exposure, migrations or other factors.