Eficácia de fungicidas químicos, biológicos e sua associação no manejo de doenças foliares e de espiga em trigo

Abstract

This study aimed to evaluate the effectiveness of chemical fungicides, biological fungicides, and their combination, applied via seed treatment (ST) and foliar spraying, in the management of foliar and head diseases in wheat (Triticum aestivum L.) under rainfed conditions. The experiment was conducted during the 2024 season at the Experimental Farm of the Federal University of Technology 3 Paraná (UTFPR), Dois Vizinhos campus, in a randomized complete block design, arranged in a 4 × 3 factorial scheme (four foliar treatments × three seed treatments), with three replications. Seed treatments included: chemical (Flutriafol + Imidacloprid), biological (inoculation with Azospirillum brasilense and Trichoderma harzianum), and the combination of both. Foliar applications were carried out at three phenological stages, namely tillering, anthesis, and grain filling, corresponding to stages 25, 64, and 77 according to the Zadoks scale. Foliar treatments included chemical active ingredients Picoxystrobin + Cyproconazole and Fenpropimorph + Pydiflumetofen, and biological agents Bacillus pumilus, Trichoderma harzianum, and Ascophyllum nodosum, as well as their combination. Phytosanitary assessments considered the severity of powdery mildew, leaf spots, leaf rust, Fusarium head blight, and wheat blast, using specific diagrammatic scales and calculating the Area Under the Disease Progress Curve (AUDPC). Data were subjected to normality analysis (Shapiro-Wilk test), data transformation when necessary, analysis of variance, and mean comparison using the Scott-Knott test at a 5% significance level, using Sisvar software. Results showed a significant effect of foliar treatments on AUDPC of powdery mildew, leaf rust severity, and head diseases, with the absence of application resulting in the highest severities and lowest yields. The foliar treatment combining biological and chemical fungicides showed the lowest severity and AUDPC indices for all diseases evaluated, standing out with a higher average yield of 4,001 kg ha⁻¹, representing a 22.7% increase compared to the control (3,262 kg ha⁻¹), and greater economic profitability, with a return of R$ 985.60 ha⁻¹ above the control, considering a price of R$ 80.00 per sack. Seed treatment alone did not significantly influence yield or phytosanitary variables, and no statistical difference was observed for yield and yield component variables.