Efeito do manejo integrado da brusone sobre componentes quantitativos e qualitativos do arroz irrigado

Abstract

Blast is a major disease in flooded rice due to its high potential to damage the crop. Blast control requires the use of integrated practices, such as cultural management, genetic and chemical methods. The main goal of this study was to assess the association of different practices, such as sowing times, cultivars and fungicide treatments to manage blast in rice crop and the effect on productive and qualitative components of flooded rice as well. The experiment was carried out in field crops located in São Sepé/RS during the 2015/16 and 2016/17 crop seasons. The experiment was arranged in randomized blocks, with split-plot design and five replications. The treatments were three sowing times, two rice cultivars and six fungicide programs sprayed accordingly to the crop phonological stages. It was assessed the leaf blast severity, panicle blast incidence, incidence of glume blotch, percentage of sterile spikelet, yield, thousand grain weight, percentage of whole grains, seed germination and vigor. There was a significant triple interaction among the factors sowing time, cultivars and chemical treatments for all evaluated variables, except for seed germination in 2015/16 crop season and seed vigor in the 2016/17 crop season. The results showed that delaying the sowing moment increases the severity and incidence of the blast in the cultivar GURI INTA CL, significantly reduced the yield, percentage of whole grains, and the physiological quality of rice seeds. Also the use of chemical methods was required to mitigate the damage caused by blast. There was no blast incidence on the IRGA 424 IR. As a result, the yield, spikelet sterility, percentage of whole grains, germination, vigor and thousand grain weight were not influenced by the application of fungicides. The study suggests that the number and timing of fungicide application to control Pyricularia oryzae in flooded rice must take in account the crop season, sowing time and cultivar resistance.