|Authors: ||G. Thébaud, C. Castelain, G. Labonne, J. Chadoeuf|
|Keywords: ||incidence curve, disease map, simulation, permutation, ESFY, apricot chlorotic leaf roll, statistics|
European stone fruit yellows (ESFY) is caused by a phytoplasma and transmitted by Cacopsylla pruni. As it is becoming a major threat in Europe for Prunus orchards, we need more knowledge on many fundamental epidemiological processes of this disease.
Up to now, the spread of ESFY in an orchard has not been analysed on a statistical basis, and the underlying mechanisms are poorly documented: How is the pathogen introduced into an orchard? How long are the incubation, latent and infectious periods for the infected trees? What is the current range of the dissemination? Can we estimate transmission parameters from the observed patterns? To begin addressing these questions, we adopted a hypothesis testing approach to the spatio-temporal correlations between the symptomatic trees.
The case study presented here is based on a long-term (17 years) survey and mapping of symptomatic trees in a group of 4 adjacent apricot orchards.
After a description of the temporal dynamics of the disease and of its spatio-temporal pattern, we tested hypotheses on the proximity between symptomatic trees.
Our results show the unevenness of disease introduction and/or symptom expression within this group of orchards.
We also demonstrate that the infected trees are too close from one to another to be the result of independent infections.
The epidemiological significance of the results is discussed.
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