Action of defense activator and foliar fungicide on the control of Asiatic rust and on yield and quality of soybean seeds

Abstract

The objective of this study was to evaluate the influence of fungicide application (PrioriXtra®, azoxystrobin + ciproconazole) and defense activator (Bion®, acibenzolar-S-methyl) on the control of Asiatic rust (Phakopsora pachyrhizi), as well as the effect of the disease on the quality of soybean seeds. The experimental design was a randomized block in factorial 4 X 10 with three replications, with four soybean breeding lines, two disease-tolerant and two susceptible and ten managements of rust control, using the products Bion®, Priori Xtra® and their combination, applied once, twice and three times, and a control. It evaluated the rate of normalized difference vegetation, productivity, mass of 1000 seeds and seed quality by means of the germination, seedling emergence, accelerated aging and seed health tests. The use of the defense activator alone in the maximum of three applications is not effective in controlling rust. The fungicide used in conjunction or not with the defense activator is effective in controlling rust and improving seed quality, when used with three foliar applications. The defoliation caused by rust affects considerably the formation of seeds, as well as productivity and also the percentage of germination and seedling emergence, and is influenced by genotype.