Técnicas de aplicação e fungicidas multissítios no controle da ferrugem asiática da soja (Phakopsora pachyrhizi)

Abstract

Soybeans have a large share of Brazilian agribusiness, with soybean being the first in the export ranking, with a turnover of US $ 27.9 billion. Despite this importance in the national context, Asian rust, caused by Phakopsora pachyrhizi Sydow, has caused high productivity losses when associated with inadequate management. In this sense, a field experiment was carried out in the municipality of Chopinzinho-PR, in order to test the efficiency of the use of multisite fungicides, mancozeb, chlorothalonil and copper oxychloride, in the control of Asian soybean rust, when associated with systemic fungicide Combined with different application techniques. The cultivar 6160RSF IPRO was used with sowing density of 300,000 ha-1 seeds, grown in plots of 84 m2. The treatments consisted of sequential applications of systemic fungicides (standard) associated with multisite fungicides, in stages R1, R3, R5.1 and R5.4. The active principles of the systemic fungicides used in the R1 stage were trifloxystrobin and prothioconazole (Fox®) at doses of 70.0 and 60.0 g i.a. ha-1, respectively; In R3 azoxystrobin and benzovindiflupir (Elatus®) were used at doses 60 and 30 g i.a. ha-1, respectively; And in stages R5.1 and R5.4, the active ingredients used were pyraclostrobin and metconazole (Opera Ultra®) at doses 65 and 40 g. i.a. ha-1, respectively. The multisite fungicides associated with the systemic ones were: mancozeb (Unizeb Gold®) at the dose of 1500 g i.a. ha-1, chlorothalonil (Bravonil Ultrex®) at dose 700 g i.a. ha-1 and copper oxychloride (CopSuper®) at a dose of 588 g. i.a. ha-1. For the spraying of the fungicides, three application techniques were used: air curtain aid at 20 km h-1, spray curtain curtain aid, and conventional (without any help at the bar). The severity of Asian rust and the disease complex was evaluated by constructing the area below the disease progress curve (AACPD) and the control efficiency for both. The yield components evaluated were: height of insertion of the first pod, plant height, number of pods per plant, number of grains per plant, mass of one thousand grains and productivity in kg ha-1. The data were submitted to analysis of variance and the means were compared by the Tukey test (p= 0.05). The multisite fungicides improved the efficiency of the systemic fungicides, providing better control for the complex of spots, reducing the AACPD in 18.9%. No significant differences were found for the different modes of application tested. Mancozeb was the multisite fungicide that obtained the best result in all analyzed variables, the association of the fungicide provided an increase of 8.6% in productivity.