Temporal and spatial characterization of Cercospora leaf spot of beet

ABSTRACT Beet cultivation has intensified due to in natura consumption and industrial processing of canned food. However, Cercospora leaf spot, caused by Cercospora beticola Sacc., is the major disease compromising the crop productivity. Few studies have been conducted on the epidemiology of the disease in Brazil; thus, the objective of the present study was to characterize the temporal and spatial progression of this disease under the cultivation conditions at the southern region of Brazil. Beet seeds of ‘Boro’ cultivar were sown in four blocks of 250 plants each. Initial disease incidence in the planting line was used for spatial analysis through the run and doublet tests, and data were analyzed based on the value (± 1.64) standardized according to Z-test at 5% probability. Subsequently, disease severity was estimated for 80 plants through a diagrammatic scale and for ten previously demarcated random plants, and data were adjusted to a nonlinear model throughout the crop cycle. The spatial pattern of the disease was over 99% at random for both tests. The disease progress curve was fitted to Gompertz model, represented by y = 0.122771 * (exp (12.830900 * exp (-0.35870 * x))). This study will serve as a model for future investigation related to the disease.