<b>The mixture volume sprayed by hydraulic and centrifugal energy nozzles for the control of Asian soybean rust

Abstract

ABSTRACT. The objective of this work was to evaluate a means of controlling ASR (Phakopsora pachyrhizi H. Sydow & P. Sydow) by applying reduced fungicide volumes in association with spray nozzles using either hydraulic or centrifugal energy. Two experiments resulted from that objective: soybean plants (Glycine max (L.) Merril) of the 'BRS Valiosa RR' cultivar were grown at the Experimental Farm of the University of São Paulo State (Unesp) in Jaboticabal, Brazil. The treatments were distributed in the field according to a randomized complete block design with four replications. The treatments consisted of the volumes of 50, 100, and 150 L ha with the droplets formed by centrifugal energy was the least efficient and resulted in the highest rust severity and the lowest grain yield.Keywords: spray nozzle, coverage, deposition, Glycine max, Phakopsora pachyrhizi, disease severity.Volume de calda em pulverização por energia hidráulica e centrífuga empregado no controle da ferrugem asiática da soja RESUMO. O objetivo da realização deste trabalho foi avaliar o controle da ferrugem asiática da soja (Phakopsora pachyrhizi H. Sydow & P. Sydow) em função do uso de menores volumes de aplicação associados a bicos de pulverização de energia hidráulica e centrífuga. Foram conduzidos dois experimentos com a cultura da soja (Glycine max (L.) Merril) cultivar "BRS Valiosa RR', em área experimental da Unesp, Câmpus de Jaboticabal, São Paulo, no delineamento de blocos ao acaso com sete tratamentos e quatro repetições. Os tratamentos foram constituídos pelos volumes de 50, 100 e 150 L ha -1 (gotas produzidas por energia hidráulica) e 17, 35 e 50 L ha -1 (gotas produzidas por energia centrífuga), mais um tratamento adicional sem aplicação do fungicida. O volume de 150 L ha -1 com gotas formadas por energia hidráulica proporcionou maior controle do patógeno pelo fungicida azoxystrobina e cyproconazole em relação aos demais tratamentos. Aplicações com o volume de 17 L ha -1 com gotas formadas por energia centrífuga foi menos eficiente com maior severidade da ferrugem asiática e menor produtividade.Palavras-chave: bico de pulverização, cobertura, deposição, Glycine max, Phakopsora pachyrhizi, severidade da doença.

Insecticide Spraying in Soybean Plants: Different Nozzles Models and Agrometeorological Conditions

“…This result corroborates with several researchers that also reported an irregular distribution of the spray solution distribution in the soybean plants, with deposits in the lower portion significantly lower than those obtained in the upper portion (Prado et al, 2010;Cunha et al, 2011;Costa et al, 2015b).…”

Spray volume deposits and fungicide efficacy on soybean rust (Phakopsora pachyrhizi)

“…2) probably contributed to reduce seed weight. The SBR disease reduces soybean yield in Brazil and other countries around the world (Scherm et al, 2009;Costa et al, 2015;Murithi et al 2016). A study published by Scherm et al (2009), showing a quantitative review of 71 fungicide efficacy trials conducted in Brazil from 2003/2004 to 2006/7, verified a yield reduction average of approximately 22% relative to the treatment without fungicide application.…”

“…The intensity of disease severity between the treatments that received fungicide applications was likely too small to be reflected in the yield difference (Table 2). A reduction in the applied spray volume may provide an increase in the sprayer operational capacity by reducing the number of refilling stops (Costa et al, 2015), allowing to spray a larger crop area (Berger-Neto et al, 2017) and consequently resulting in a reduction of plant protection costs. However, ground applications with lower spray volume may be economically worthwhile, since the biological efficiency of pesticides does not appear to be compromised by volume reductions.…”

“…Despite many studies on the development of soybean cultivars resistant to P. pachyrhizi (Langenbach et al, 2016;Vuong et al, 2016;Childs et al 2018), control has been difficult due to the variability and dynamic plasticity of the rust population, varying in virulence and genetic composition (Murithi et al, 2016). One of the most effective management strategies to suppress SBR severity and to reduce yield loss is the application of sequential fungicides (Scherm et al, 2009;Costa et al, 2015;Prado et al, 2015). The correct choice of fungicides, as well as many other parameters, is essential for satisfactory SBR control (Mueller et al, 2009).…”

“…In previous studies, the range of spray volumes from 60 to 187 L ha -1 did not impact the amount of deposits throughout the soybean canopy (Derksen et al, 2008;Prado et al, 2015); however, a reduction of the spray volume appears to not work well when fungicides are applied to control SBR. According to Prado et al (2015) and Costa et al (2015), control of SBR is reduced and yield losses increase as the spray volume decreases. Excessive reductions in spray volume should be carefully considered to avoid inadequate control of SBR and increased yield losses.…”