Application of geostatistics in studying epidemiology of hazelnut diseases: a case study.

Abstract New information management technologies, such as geographic information techniques (GIS) and geostatistics, have been already applied in the past in the study of spatially related data in plant pathology. In particular, geostatistics offer a mean to describe spatial continuity, an essential feature of many natural phenomena, such as the spreading of a plant disease. Various hazelnut diseases and their epidemiology are susceptible to be investigated by means of these technologies. “Kriging” is a regression technique used for the estimation or interpolation of spatially located and spatially correlated data. This work shows an example of the Kriging method applied to the study of the epidemiology of the Dieback hazelnut on Monti Cimini (Central Italy) in 6 years of observation. This method, properly adapted, is susceptible to be also applied to the study of other hazelnut diseases and even to several spatial phenomena interesting the culture. The hazelnut Dieback is a bacterial disease which has been affecting hazelnut orchards in Province of Viterbo since the 1980s. In the last years, many aspects were clarified but, on the other hand, other questions still remain unsolved about the epidemiology, such as the particular incidence of the disease on areas characterised by specific climatic features. The Kriging geostatistic method was applied in order to better describe the progression of the disease in the last years. A major concentration of diseased and dead plants was observed in two peculiar areas of hazelnut cultivation: the first one on the outer part of the volcanic caldera of Lake of Vico, and the second one on the northern inner part of the caldera itself. The disease spread mainly in areas which were still interested by the hazelnut dieback since its first appearance. The results of the semivariogram parameters show a good spatial autocorrelation, especially in the period 1998-2000 and for the year 2003. INTRODUCTION