Desempenho de diferentes modelos de pontas de pulverização no controle da ferrugem asiática da soja

Abstract

Spraying nozzles affect the produced droplet uniformity quality and the amount of spray solution spread per unit in the area. This work aimed to check the performance of different spraying nozzles on the deposition of spray droplets on the plant canopy and the effect on Soybean Asian rust control application. Two experiments were carried out: the first harvest in 2013/2014 in Água Santa/RS and the second one in 2014/2015 in Passo Fundo/RS. Soybean cultivar Brasmax Ativa RR was used, with 0.45cm row spacing and a population of 377,000 ha per plant. The experiment design was in randomized block with eleven treatments and three replications in each treatment. The treatments constitute of ten spraying nozzle models (hollow cone, flat-fan, turbo twin flat-fan and with and without air induction turbo flat-fan), keeping control without fungicide application. Applications were performed with a portable pressure sprayer pressurized by CO 2,regulated to apply a spraying volume of 150 L ha. During fungicide application, water sensitive paper was used in different positions on the soybean canopy. To determine the disease uredines/cm2, four plants were sampled to identify in each leaflet the number of uridine/ cm 2 .In all sampled leaflets, four points with 1.0 cm-2 were randomly marked to determine the uredines number/cm2 With the uridine number/cm 2, the area under the disease progress curve (AUDPC) was integrated. The percentage of control was obtained comparing AUCPC to control with the treatments AUCPD. After harvesting the grain yield was determined. The data were submitted to analysis of variance by Turkey test at 5% probability. It was concluded that in two harvesting seasons the nozzles Guardian 120015 and Airmix 10015 with median spray droplet characteristics showed better spray liquid deposition on the crop canopy (inferior and middle portion), higher droplet uniformity, lower AUDPC and consequently better Soybean Rust control.