Preliminary study on micro area based spatial distribution of Monilinia fructigena in an organic apple orchard

Spatial aspects of brown rot development in fruit orchards have received considerably less attention than temporal dynamics. Two-dimensional spatial patterns have been investigated by van Leeuwen et al. (2000) and Xu et al. (2001) in pome fruits. In general, these studies showed that infected trees were spatially clustered within orchard rows, with variable intensity of disease among individual trees. Although spatial patterns were more pronounced in pear (Pyrus communis) than in apple (Malus domestica) orchards, wounding of the fruit by birds, insect damage or growth cracks was considered an influential source of the spatial pattern in both species. In a separate study, Elmer et al. (1998) examined the twodimensional spatial pattern of Monilinia fructicola strains resistant to dicarboximide fungicide in peach and nectarine orchards, reporting that resistant strains were mostly restricted to individual trees with no spatio-temporal correlations from year to year of trees harbouring resistant strains. Previous studies examining spatial disease patterns within tree canopies either divided the canopy into layers (Holb and Scherm, 2007) or quadrats (Batzer et al., 2008; Spósito et al., 2008). However, an important limitation of using such stratification is that the associated grouping of data may fail to capture fine-scale patterns within each block. In a recent pilot study, Everhart et al. (2011) used a digitizer to map different brown rot symptom types (blossom blight, shoot blight, and twig cankers) caused by the fungal plant pathogen M. laxa in individual sour cherry canopies. In this study, we aimed to report a preliminary study on micro area based spatial distribution of M. fructigena in an organic apple orchard. Materials and methods