White mold for soybean crop in Brazil as affect by climate and agricultural management conditions

In Brazil, epidemics of white mold in field crops of soybean have frequently and significantly compromised crop yield and quality. The aim of the current research was to assess epidemiology of white mold (Sclerotinia sclerotiorum) on soybean crop grown at Arapoti, PR, Brazil, utilizing data related to plant populations, row spacings and local meteorological factors. The experiment was conducted in a naturally infested area. The experimental design adopted was a randomized block distributed 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), totaling 16 treatments and 4 replications. In the current study we performed four assessments of incidence and severity. The temporal analysis of the epidemic was carried out from the area under the disease progress curve. 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, revealing a mean coefficient of determination of 0.971. Either for incidence or for severity, air temperature was considered to be the environmental factor most affecting the progress of the disease in production fields of soybean. 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.