Influence of spraying tips on the efficiency of chemical control of soybean rust

Abstract

Asian rust is responsible for significant reductions in soybean yield. The application of fungicide is the main method of control of this disease, and to maintain the efficiency of phytosanitary treatment it is necessary to know several features of the application technology. Spray tips are fundamental for the quality of phytosanitary products application and exert a direct influence on spraying efficiency. The objective of this study was to evaluate the efficiency of different spray tips in spray deposition and leaf cover in the lower, middle and upper thirds of soybean plants in three distinct phenological stages. Another objective was to evaluate the efficiency of the commercial mixture trifloxystrobin + prothioconazole (FOX®), applied by different spray tips, in the control of Asian rust and soybean yield. The experiment was conducted for two agricultural years, and six spray tips were evaluated: TT 11001, TTJ60 11002, TXA 8003, 30HCX 12, GRD120 02 and GAT11002 in three fungicide applications with intervals of 15 days, in the phenological stages V6–V7, R1 and R4, using the working pressure of 5 bar and spray volume of 200 L ha−1. The coverage and deposition of spray promoted by all spray tips, in the three phenological stages of soybeans, were sufficient to provide satisfactory control of rust, with means of disease severity ranging from 1.69 to 4.70%, compared to the control (mean severity of 54.34%), without significant loss of yield in the sprayed plots. All evaluated spray tips can be recommended for use in spraying FOX® fungicide (trifloxystrobin + prothioconazole) in soybean crop for Asian rust control, when the spray volume applied is 200 L ha−1.