RESUMO:A eficiência do controle químico da ferrugem-asiática da soja (FAS), além de outros fatores, está associada ao uso da técnica de aplicação de fungicida mais adequada. O trabalho teve por objetivo avaliar tecnologias de aplicação sobre os depósitos da pulverização e controle da FAS nos anos agrícolas de 2009-2010 e 2010-2011. O delineamento experimental foi em blocos casualizados, e os tratamentos distribuídos no esquema fatorial 3x2 (três taxas de aplicação: 60; 110 e 160 L ha -1 com e sem adição de surfactante siliconado) sobre os depósitos da pulverização, usando como marcador o corante Azul Brilhante, em quatro repetições (Experimento 1). Para avaliação da severidade da doença, peso de mil grãos (PMG) e produtividade, foi adotado o mesmo delineamento do primeiro experimento, com acréscimo de uma testemunha (3x2+1), utilizando a mistura fungicida epoxiconazole associado com azoxistrobina, com quatro repetições (Experimento 2). As taxas de aplicação e o uso do surfactante não influenciaram os níveis dos depósitos da pulverização nas folhas das partes mediana e inferior da planta. Pulverização com a mistura fungicida na taxa de 160 L ha -1 proporcionou maior controle da FAS e maior produtividade no ano agrícola de 2010-2011. O controle químico com fungicida, na taxa de aplicação adequada ao estádio de desenvolvimento da planta, torna-se indispensável para a garantia da produtividade na cultura da soja. PALAVRAS-CHAVE: adjuvantes, depósitos da pulverização, tecnologia de aplicação. EFFECTS OF SILICONE SURFACTANT AND APPLICATION RATES ON SPRAY DEPOSITION AND SOYBEAN RUST CONTROLABSTRACT: Chemical control efficiency of Asian soybean rust (ASR), besides other factors, is associated with an appropriate fungicide application technique. This study aimed to evaluate the effect of different application technologies on spray deposition and ASR control in 2009-2010 and 2010-2011 crop seasons. The experimental design was a completely randomized block with four replications in a 3x2 factorial scheme. Three application rates were tested (60, 110 and 160 L ha -1 ) with and without silicone surfactant addition using a Brilliant Blue dye tracer in spray solution to analyze deposition (Experiment 1). For disease severity, thousand grain weight (TGW) and yield were evaluated on the same experimental design as used in Experiment 1 plus a control (3x2+1). It was used the fungicide mixture of azoxystrobin and epoxiconazol in four replications against ASR (Experiment 2). Application rates and surfactant use did not affect spray deposit levels on middle and bottom plant parts. The fungicide mixture at 160 L ha -1 was more effective for disease control and showed a greater yield in the 2010-2011 crop season. Chemical control with fungicides and application rates proper to the plant growing stage become essential to ensure a good soybean yield.

Accurate application of pesticides is difficult for crops with dense leaves, such as soybean crops. To improve spray deposits on the lower leaves of soybean plants, the aim of this study is to build a canopy opener (CO) from a previously developed prototype and to assess its practical application and efficiency on soybean crops. Laboratory experiments were conducted to determine the amount of spray deposits on the top and the lower leaves using a Brilliant Blue dye. The influence of the CO device on the number of flowers knocked down during spraying was also investigated. The data showed that the use of the CO attached to the spray boom enabled more spray deposits on the lower leaves and less spray deposits on the upper leaves compared with conventional spraying. The CO device did not influence the falling of flowers or the damage to the soybean plants. The construction of the CO device proved to be a feasible alternative, which could be used primarily by small-scale soybean producers, with the goal of obtaining larger spray deposits on the lower leaves of soybean plants.

Soybean rust (SBR), caused by Phakopsora pachyrhizi, is one of the most destructive fungal diseases affecting soybean yields in many countries. Fungicide application methods that provide better SBR control efficacy may reduce soybean losses due to this disease. We investigated the effects of spray volumes applying the fungicide pyraclostrobin plus epoxiconazol at 133 + 50 g a.i. ha-1 by a conventional sprayer (CS) and an air-assisted sprayer (AAS). Field experiments were conducted comparing the effects of spray volumes of 110, 160, and 210 L ha-1 and two application techniques (CS and AAS) on spray deposits and SBR control. Fungicide efficacies were measured by disease severity, thousand seed weight, and yield. Correlations between disease severity and yield were also assessed. All treatments were applied with an Advance 2000 AM18 sprayer. In general, SBR disease and yield did not differ significantly when fungicide applications were applied with AAS compared to CS. Increasing the spray volume from 110 to 210 L ha-1 did not increase spray deposit coverage on soybean leaves. Low disease severity was obtained by fungicide applications using a spray volume of 210 L ha-1. Safe recommendations of ground spray volumes for SBR control should be between 160 and 210 L ha-1, using hydraulic nozzles.