Management of foliar application of fungicides to enhance physiological and sanitary quality of soybean seeds

Abstract

Controlling disease in the soybean crop is essential for obtaining high quality seeds and high yield. This leads the producer to increase the number of fungicide applications as a preventive measure. The aim of this study was to evaluate soybean response to increase in the number of foliar applications of different chemical fungicides during crop development to enhance the physiological and sanitary quality of soybean seeds. The experiment was performed in the state of Minas Gerais, Brazil, in two environments (Ijaci and Lavras) in the 2014/15 crop year, with the cultivar BRSMG 850G RR . The field experiment was conducted in randomized blocks in split-plots, with three replications. The plots were composed of the number of applications (0, 1, 2, 3, 4 and 5 times). The applications started at the R 1 stage (beginning of bloom), with a 15-day interval to the next application (R 1 ; R 1 +15d; R 1 +30d; R 1 +45d; R 1 +60d). The split-plots were constituted by the different chemical fungicides (Elatus ® , Fox ® , Opera ® , Orkestra ®, and an unregistered product -BAS -702). Seeds were evaluated soon after harvest and after eight months of storage. The following characteristics were evaluated: seed water content, germination in paper and sand substrates, emergence, emergence speed index, mechanical damage in the sodium hypochlorite test, electrical conductivity, accelerated aging, seed vigor and viability by the tetrazolium test, and seed health, using a completely randomized design. Regardless of which fungicide was used, an increase in the number of foliar applications of fungicides, up to five applications, leads to an increase in the physiological and sanitary quality of soybean seeds, both those newly harvested and those stored for eight months. However, Fox ® fungicide (trifloxystrobin + prothioconazole) applied on the leaf during the reproductive stages of the soybean crop brought about the best results in the physiological quality of newly harvested seeds and seeds stored for eight months, as well as in the sanitary quality of newly harvested seeds.