Influência do horário de aplicação de fungicidas sobre o progresso de ferrugem asiática e produtividade de soja

Abstract

The objective of this study was to evaluate the severity of Asian rust in soybean due to different fungicide application schedules. The experiment was conducted in Erechim/RS at the Federal University of Fronteira Sul, 2018/19 crop season, using a randomized complete block design, with six treatments and four replicates, being these different times of application of fungicide: T1) control (without application); T2) application at 6:00 a.m.; T3) application at 8:00 a.m.; T4) application at 10:00 a.m.; T5) application at 6:00 p.m.; T6) application at 8:00 p.m. Phenological stages in which the applications were carried out and the respective fungicides to control Asian rust in all treatments except the control were: V6) bixafen + prothioconazole + trifloxystrobin (62.2 + 87 + 75 g a.i. ha-1); R1 and R5.1) trifloxystrobin + prothioconazole (60 + 70 g a.i. ha-1) + mancozeb (750 g a.i. ha-1); and R6) trifloxystrobin + cyproconazole (75 + 32 g ia ha-1). During the conduction of the experiment, for the calculation of area under disease progress curve (AUDPC), the severity of the disease was evaluated, with intervals of 7 days after the identification of the pathogen, in a random sample of five trifolia per plot. After harvesting, the yield components were determined, considering the number of grains per plant, the weight of one thousand grains (g), and the total productivity (kg ha-1). It can be concluded that in the 2018/19 crop season, for cv. DM 5958 RSF IPRO, the applications of fungicides carried out at 6:00 a.m, 8:00 a.m. and 10:00 a.m. were the most efficient for the control of Asian soybean rust, being this superior 83.9%. The application of fungicides at 10:00 a.m. implies a productivity gain equivalent to 644.2 kg ha-1.