New insights on Scaphoideus titanus biology and their implications for integrated pest management

The Nearctic leafhopper Scaphoideus titanus is known to be the main vector of Flavescence doree phytoplasma (FDP), a serious disease of the grapevine in temperate European areas. Adult lifespan and oviposition rate were investigated under semi-natural conditions to assess potential fecundity of this species. Egg load was detected under field conditions in North Italy. Females lived longer than males, with a sex ratio in their favour during the late season when they are still able to lay eggs. Both sexes have a high average lifespan, females can live over 60 days whilst males over 40 days. Furthermore, 25% of the females lived over 70 days, and laid an average of 60-65 eggs. A number of approximately 70 to 130 eggs was laid by 25% females. The comparison between the egg load trend and the oviposition rate shows that both indices remain constant until September and then decrease in the following months. The presence of the vector was detected until late season in the vineyards. In fact, some females with mature eggs were collected until October 30th, whilst in seminatural condition few individuals were able to lay eggs until the end October to early November. This research shows as S. titanus biological parameters have been largely underestimated so far. A serious implication of the high longevity is the prolongation of the adult inoculation period, and a temporal expansion of the risk of infecting the vineyards no longer protected by insecticide treatments. This suggests to reconsider the phytosanitary management of the vineyards after harvesting.