Temporal and spatial characterization of Botrytis leaf blight of onion

ABSTRACT Onion cultivation has intensified due to in natura consumption and industrial processing. However, Botrytis leaf blight (Botrytis squamosa Walker) is the main disease in the seedling period and has compromised the crop. As the epidemiology of the disease in Brazil is unknown, the objective of this study was to characterize the temporal and spatial progression of this disease under cultivation conditions in the southern region of Brazil. Three grams of onion seeds of the cultivar EMPASC 352- Bola Precoce were sown in eight blocks of one square meter each. The initial incidence of the disease at the planting site was used for the spatial analysis through the negative binomial test. The severity of the disease during the cultivation was analyzed based on the percentage of leaf area affected by the disease in ten randomized plants previously demarcated in each replicate and the severity data were adjusted to a nonlinear model throughout the crop cycle. The spatial pattern of the disease was random and the disease progress curve was fitted to the Gompertz model, represented by y = 0.51830 * (exp (5.95660 * exp (-0.47392 * x))). This study will serve as a model for research related to the disease.