Spray solution deposition and Asian rust control in soybean cultivars /Deposicao de calda e controle da ferrugem asiatica em cultivares de soja

The control of Asian soybean rust depends on fungicide efficacy and the application technology; however, the leaf architecture of soybean cultivars may also interfere in disease control. This study aimed to evaluate Asian rust control and fungicide deposition using spray nozzles in three soybean cultivars. A randomized block design was used, with treatments arranged in a split-plot scheme; the plots were three soybean cultivars (SYN 1561 IPRO, M6410 IPRO, and M6210 IPRO) and the subplots three spray nozzles (11002 BD, AIXR 110015 and TTJ60 11002), in addition to a control with no fungicide application, and four replicates. The volume median diameter, droplet coverage, leaf area index, area under the disease progress curve, 1,000-grain weight and crop yield were evaluated. The 11002BD and AIXR11005 nozzles provided better spray deposition in cultivars with lower leaf area indexes at the R1 phenological stage. Nozzles 11002BD, AIXR110015 and TTJ60 ensured better management of Asian rust than that of the control treatment, regardless of leaf area index. Cultivar SYN1561 obtained the largest grain yield and highest leaf area index in the season with the highest rainfall, regardless of the spray nozzle used. Key words: Glycine max, Phakopsora pachyrhizi, application technology, droplet density, fungicides O controle da ferrugem asiatica da soja depende da eficacia do fungicida e da tecnologia de aplicacao empregada, entretanto, a arquitetura foliar de cada cultivar de soja tambem pode ser um fator a interferir no controle da doenca. O objetivo do estudo foi avaliar a deposicao de calda fungicida e o controle da ferrugem asiatica da soja utilizando pontas de pulverizacao em tres cultivares de soja. O delineamento experimental utilizado foi em blocos ao acaso, com tratamentos arranjados no esquema de parcelas subdivididas, em que as parcelas eram tres cultivares de soja (SYN 1561 IPRO, M6410 IPRO e M6210 IPRO) e as subparcelas tres pontas de pulverizacao (11002 BD, AIXR 110015 e TTJ60 11002), e uma testemunha sem aplicacao, com quatro repeticoes. Foram avaliados o diametro mediano volumetrico, cobertura de gotas, indice de area foliar (IAF), area abaixo da curva de progresso da doenca, massa de 1000 graos e produtividade da soja. Os bicos 11002BD e AIXR11005 fornecem melhor deposicao de calda naquelas cultivares com menores indices de area de foliar, no estagio fenologico da soja R1. Os bicos 11002BD, AIXR110015 e TTJ60 fornecem controle da ferrugem asiatica comp