APLICAÇÃO DE FUNGICIDAS MULTISSÍTIOS EM MISTURA E DE FORMA ISOLADA NO MANEJO DE RESISTÊNCIA DE Phakopsora pachyrhizi NA SOJA

Abstract

Plant diseases are among the main factors that limit high yields in any cutlivar. Asian soybean rust, caused by the fungus Phakopsora pachyrhizi, is the most severe disease and can cause yield reductions of up to 80%. Other diseases such as powdery mildew, caused by Microsphaera diffusa and brown spot, caused by the fungus Septoria glycines are also very important in the crop, as they can lead to significant losses in productivity. Chemical control is currently the most viable tool to prevent losses, but a lower sensitivity of fungi to fungicides has been reported in Brazil. The objective of this work is to research new tools that help in the management of resistance to P. pachyrhizi along with other diseases through chemical control with the addition of multisite fungicides in mixture and isolation. Two experiments were carried out in the city of Uberlândia-MG, in the 2018/2019 crop. The soybean cultivars used in first and second trial were SYN1378C and TMG7063 respectively. The randomized block design used, was composed of 16 treatments and 4. A total of six fungicides, namely: Elatus [200 g pc / ha] (EL), Cypress [300 ml pc / ha] (CY), Bravonil [1.5 L pc / ha] (CTN), Trifloxystrobin + Ciproconazole [200 mL pc / ha] (SM), Mancozeb [1500 g pc / ha] (MZB) and Protioconazole + Trifloxystrobin [400 mL pc / ha] (FOX), were used, which, in different combinations, made up the 16 treatments. The treatments were applied from 38 days after soybean emergence, with application intervals of 7 and 14 days. Each experimental plot contained an area of 18 m², 6 meters long, 3 meters wide and 50 cm line spacing. Evaluations were performed weekly, and severity scores were given according to the diagrammatic scale established for the crop, performed on 10 leaves of the middle third and the lower third of the plant. Yield was measured at the end of the experiment, with a 4.5 m² harvest of the plot. By analyzing the results, it was found that none of the evaluated products acted in an eradicating way, preventing the development of the diseases analyzed. However, in all treatments there was a reduction in severity, favoring the productivity of both experiments. For rust the treatments with the best performance in controlling the pathogen were T16, T5, T13, T14 and T11, and the combined use of systemic and contact products in the initial period of disease development was more interesting. For the control of powdery mildew and brown spot the use of alternate isolated products and in the early stages of disease development showed more promising, highlighting in this work Treatment 10. The results showed that the use of multisite fungicides in mixture or isolation in the control of fungal diseases in soybean crop it is efficient, ensuring the productive capacity of the evaluated cultivars.

Keywords: Glycine max; Chemical control; Asian soybean rust (ASR); Microsphaera diffusa; Septoria glycines.