Rotação de culturas, monocultivo e aplicação de fungicidas para controle de mancha amarela em trigo

Abstract

Wheat is an important agricultural crop and meets the food needs of humans and animals. However, diseases such as tan spot compromise crop productivity. The objective was to evaluate the effectiveness of fungicide application in the control of tan spot in wheat, under cultivation environments with and without crop rotation, and the effects on disease severity, yield components and wheat productivity. The experiment was carried out in the Experimental Area and in the Plant Pathology Laboratory of the Universidade Federal da Fronteira Sul (UFFS), Campus Erechim/RS, in the 2022 crop season. The cultivar used was TBIO NOBLE conducted in a randomized block design with 5 treatments and 4 replications. Two environments were evaluated, namely: i) with crop rotation; and ii) no crop rotation (wheat over wheat). Fungicide treatments consisted of: T1) control, without fungicide application; T2) azoxystrobin + cyproconazole (1st and 2nd applications); bixafem + prothioconazole + trifloxystrobin (3rd application); and azoxystrobin + cyproconazole + mancozeb (4th application); T3) azoxystrobin + cyproconazole + propiconazole (1st and 2nd applications); T4) azoxystrobin + cyproconazole + iprodione (1st and 2nd applications); and T5) azoxystrobin + cyproconazole + pidiflumetofen (1st and 2nd applications). The 3rd and 4th application, for T3, T4 and T5 were the same as those described in T2. Applications were positioned at full tillering, stem elongation, flowering, and grain filling stages of wheat. The variables analyzed were: severity (%) of tan spot in wheat, control (%), hectoliter weight (HW), ear length (cm), number of full and dull grains per ear, thousand-grain weight (TGW, g) and productivity (kg ha-1). In treatments with fungicide applications (T2 to T5) control of 65.6% (with crop rotation) and 69.2% (without rotation) was obtained; the treatment that showed the best control was T5 (85% and 79%) both with and without crop rotation, respectively. For ear length, the treatments did not differ among themselves in the conditions of crop rotation and monoculture. As for the number of full and dull grains per ear, there was no statistical difference between the evaluated environments. The use of fungicides ensured HW greater than 79 for both rotation and monoculture. There was a statistical difference between the cultivation environments for the TGW variable, with the highest weight obtained in T5 (40.2 g), in an environment with crop rotation; this treatment contained the carboxamide pidiflumetofem. The mean TGW for cv. TBIO Noble is 33 g, so this treatment exceeded that average. At T5 and when wheat was grown with crop rotation, there was also the highest productivity, along with T3. These treatments provide an increment of 17 sc ha-1 and 5 sc ha-1 in relation to T4, which had the lowest productivity among treatments containing fungicides.