Controle quimico da ferrugem asiatica da soja em cultivares resistente e suscetivel a Phakopsora pachyrhizi Syd. & P. Syd

Abstract

A number of diseases are present in the soybean crop, among them, Asian rust is considered the main and with great potential to cause damages to the production where, in severe attacks, the disease can cause early defoliation, compromising the photosynthetic activity of the plant and, consequently, the filling of grains. The objective of this work was to evaluate the efficacy of different fungicides in mixed formulations in the control of Asian soybean rust and others diseases in the 2017/2018 crop in resistant and susceptible cultivars, as well as its effect on the germination of Phakopsora pachyrhizi uredospores. Developed at the Federal University of Grande Dourados, this work consisted of two stages. In the first, in the field, the cultivars BMX-POTENCIA RR and TMG 7063 IPRO were sown. Fungicide applications were performed with CO2 pressurized costal sprayer, coupled to a bar provided with four spray nozzles spaced 0.5 m. The experimental design was a randomized complete block design in a 2x5 factorial arrangement, where the fungicide applications were performed in the R4 and R6 stages. The second assay was carried out at the Laboratory of Agricultural Microbiology and Phytopathology, where 1 ml of a suspension of P. pachyrhizi uredospores containing 6.43x104 spores were transferred to disposable petri dishes in contact with fungicide syrup, then incubated in a chamber of germination type BOD at 24o C (± 1o) in the continuous dark for 15 hours. The experimental design was completely randomized, with five replications. There was no significant difference in soybean rust control using different mixed formulations in the two soybean cultivars. The association of mancozeb in mixed formulations significantly reduced the percentage of germination of P. pachyrhizi uredospores.