Improved knowledge on key epidemiological parameters to optimize Sharka management strategies

Sharka is a major viral disease of stone fruits (Prunus) worldwide, reducing both fruit quality and yield. Caused by Plum pox virus (PPV, family Potyviridae, genus Potyvirus), the disease is spread over long distances by the propagation and transport of infected plant material and locally by aphids in a non-persistent manner. Apart from strategies to breed resistant, hypersensitive or tolerant cultivars that are not yet available for all Prunus species, prophylaxis, surveillance and the removal of symptomatic trees remain the only options to mitigate the impact of Sharka and to prevent the spread of new PPV variants. The design of sustainable management strategies, especially in the context of the recent European deregulation of PPV, requires a good understanding of the factors driving virus evolution and disease dynamics, from the tree to the landscape scales. To gain insights into the processes and parameters underlying epidemic dynamics, we use complementary approaches including experiments under controlled conditions, field surveys, and parameter estimations from disease surveillance databases. We work on key epidemiological parameters acting at the scale of the tree (e.g., interactions between PPV strains and Prunus species, duration of the latent period, aphid transmission rates) or at the landscape scale (aphid dispersal function). These parameters are integrated in a modeling framework to simulate epidemics in different types of landscapes and to identify the most effective Sharka management strategies.