Aplicações de fungicidas no estádio V5 e o impacto no manejo de doenças e na produtividade do milho segunda safra

Abstract

The leaf’s area reduction due to pathologies in maize results in lower photosynthetic rates causing a deficit in yields. As a result of the increase in corn second season farming, the occurrence of necrotrophic pathogens, such as Cercospora zeae maydis, Exserohilum turcicum and Bipolaris maydis has become typical. The use of resistant hybrids linked to fungicides use at different times is a positive strategy in the mitigation of foliar diseases. High-tech producers adopt three applications, corresponding to the phenological stages V8, VT and R2. However, in the second season, conditions of high humidity and temperature favor the early incidence of foliar pathologies, making it necessary to anticipate the application of fungicides. The objective of this work was to evaluate the impact on disease management and corn second season yield by fungicide applications from the V5 stage. Trials 1 (E1 – STATUS VIP3) and 2 (E2 – SUPREMO VIP3) were conducted in the second season of the 2021/2022 agricultural year. The experimental design adopted in both tests was randomized blocks (RB). In E1, 4 treatments were studied with 12 repetitions for the productivity attribute and 6 for the other characteristics. The treatments consisted of fungicides from the chemical groups of triazoles, strobilurins and isoftalonitriles applied at different times. In E2, 5 treatments composed of fungicides from the chemical groups of triazoles, strobilurins, isoftalonitriles and benzimidazoles, applied at different times, were studied. In this test, all evaluated characters were analyzed with 6 replications. The characteristics of final plant population, plant height, ear insertion height, green leaf area, severity of leaf diseases and yield were evaluated. Using the SISVAR statistical program, analysis of variance and Tukey's test at 0.05 significance were performed. Under the conditions of the present work, it was verified that, regardless of the hybrid studied, the applications from the V5 stage onwards were positive, with emphasis on the T4 (E1) (Difenoconazole + Cyproconazole V5 / Azoxystrobin + Difenoconazole V8, VT and R2 / Chlorothalonil VT-R2) and T5 (E2) (Carbendazim + Tebuconazole V5 / Azoxystrobin + Difenoconazole V8, VT and R2 / Chlorothalonil VT-R2) treatments.