Época de semeadura combinada à aplicação de fungicidas sobre o progresso de ferrugem asiática e produtividade da soja

Abstract

All agricultural cultivation is subject to both quantitative and qualitative losses. In soybean, Asian rust is among the major diseases and is caused by the fungus Phakopsora pachyrhizi. As far as disease control is concerned, the cultural method advocates the adoption of practices such as scheduling of the sowing season that may interfere in the development of Asian rust. The objective of this work was to evaluate the progress of Asian rust and soybean yield in relation to different sowing times, combined or not with fungicide application. The experiment was conducted at Federal University of Fronteira Sul - Campus Erechim (Rio Grande do Sul, Brazil), in the 2017/18 and 2018/19 crops seasons, with cv. DM 53i54 RSF IPRO. The design was a randomized complete block design, with subdivided plots and four replications. The sowing times (S1, S2, S3 and S4) were arranged in the main plot. The application or not (control) of fungicides, in the respective stages were arranged in the subplots: V6 - trifloxystrobin + prothioconazole (60 + 70 g i.a. ha-1); R1-azoxystrobin + benzovindiflupir (75 + 37.5 g i.a. ha-1); R5.1-azoxystrobin + benzovindiflupir (75 + 37.5 g i.a. ha-1); and R6-fluxapiroxad + pyraclostrobin (50.1 + 99.9 g a.i. ha-1). The severity (%) of Asian rust was estimated by estimating the area below the disease progress curve (AUDPC) and control (%); number of pods per plant; number of grains per plant; weight of one thousand grains (g) and productivity (kg ha-1). With the application of fungicides, there was an increase in productivity in the first sowing times in relation to later sowing. This increase worsened even more when compared to the latter without the use of fungicide. Therefore to reconcile the cultural control with the chemical, anticipating the sowing of the soybean, reduces the damage caused by the Asian rust and provides a greater yield for the crop.