Fungicidas foliares e a doença ferrugem asiática na produção e na qualidade de sementes de soja

Abstract

Unfavorable weather conditions during late soybean maturation have caused problems in seed quality due to "forced maturation" or premature plant death, which can result in green seeds. This study aimed to evaluate the effect of fungicides and rust disease on soybean seed yield and quality, focusing on the occurrence of green seeds. The treatments included a control and fungicide applications of flutriafol + thiophanate- methyl, pyraclostrobin + epoxiconazole and metconazole, in the R2 and R5.1 growth stages, individually and also in combined applications. The experiments were carried out in the field at Londrina-PR, during the 2007/08 and 2008/09 crop cycles with the Coodetec 206 cultivar. The following evaluations were made: rust disease severity using a diagrammatic scale, productivity, seed weight and visual assessment of the percentage of green seed. Seed quality was evaluated from germination, tetrazolium, accelerated aging and electrical conductivity tests. Analyses were performed immediately after harvest and after six months of storage. The fluorescence chlorophyll test was carried out in the second crop seeds. The experimental design was randomized blocks with seven treatments and four blocks for each crop. Means were compared by the Tukey test at 5% probability. The fungicide, that efficiently controlled soybean rust did not affect production and seed quality or the occurrence of green seed. Under favorable weather conditions for seed maturation, the severity of soybean Asiatic rust interferes with production but does not influence seed physiological potential. Soybean rust associated with unfavorable weather conditions during the final stage of maturation results in green soybean seeds that reduce vigor after storage.