No abstract

White mould (Sclerotinia sclerotiorum) is a damaging disease of soybean crops in Brazil. Within-field spatial analyses of white mould disease and inoculum, as well as yield components at the field level may provide insights into their relationship, but this information is lacking in the country. During three years, spatially explicit within-field data on white mould and soybean stand and yield were measured at three fields, with sizes ranging from 4 to 12 ha, located in the Campos Gerais region of Paraná State, Brazil and all naturally infested with sclerotia. Crop stand, white mould incidence and severity, soybean yield and sclerotia collected at harvest were assessed in quadrats of 7.2 m 2 distant from each other by 8 to 50 m. Soilborne sclerotia were counted in four quadrats (0.25 m 2 and 0.05 m depth) at each sampling point. The semivariograms fitted the pure nugget effect, linear, spherical, and exponential models. The pure nugget model best fitted sclerotia data, suggesting a random distribution. Significant and positive associations were found between disease incidence and sclerotia amount at harvest, which were both negative associated with yield.

No abstract

Currently the soybean crop is affected by the white mold (Sclerotinia sclerotiorum). The disease can reduce the crop yield and quality and decrease the prices of agricultural lands. The aim of the current research was to assess epidemiology of white mold on soybean crop grown at Arapoti, PR, Brazil, utilizing data related to agricultural practices and local meteorological factors. The experiment was conducted in a naturally infested area. The soybean crop was sown on October 18th, 2011. The experimental design adopted herein was a randomized block in a factorial combination with 4 row spacings (0.35, 0.45, 0.60, 0.75 m) and 4 plant populations (150, 200, 250, 300 thousand plants per hectare) and 4 replications. The temporal analysis of the epidemic was evaluated using mathematical models, such as Logistics, Monomolecular and Gompertz, in order to determine the best model that described the progress of the disease as a function of local meteorological elements. For the incidence data it has been shown that both logistic and monomolecular models were those that were best fitted to the experimental data. For severity, the best model related to the experimental data was the logistic one. Either for incidence or for severity, air temperature was considered to be the environmental factor most affecting the progress of the disease. The variability in the apparent infection rates of white mold on soybean was not affected by different row spacings and plant populations; therefore, suggesting that macroclimatic variations prevailed in such a fashion to mitigate the effect of cultural practices adopted in the field.