Levedura, indutores de resistência e fungicidas multissítios no controle de doenças no algodoeiro

Abstract

Brazilian cotton has reached the highest product ceiling and stands out at the world level for the volume of production produced and its quality. However, there are still several problems in the cotton cultivation system, among them the control of diseases such as those caused by the fungi Ramulariopsis gossypii and Corynespora cassiicola that cause productivity losses in the cotton crop in the State of Mato Grosso. Farmers have been using commercial chemical fungicides, but without satisfactory control, in some cases mainly when related to the resistance of phytopathogens. Thus, this work aimed to determine the effect of the association of yeast (Pichia sp.), resistance inducers (salicylic acid and copper micronutrient) and multisite fungicides (Mancozeb, Copper Oxychloride and Chlorothalonil) in the control of Ramularia leaf spot (R. gossypii) and target spot (C. cassiicola), in cotton. The experiment was carried out in the municipality of Sorriso-MT, at 12 ° 34'33.13'' S and 55 ° 41'37.88'' W, altitude of 378 meters, during the second crop of the agricultural year 2019/20. The experimental design was in randomized blocks, with five replications and eight treatments. Seven sequential applications of the mixtures with treatments were carried out, at intervals of 15 days from thirty days after the emergence of the culture (30 DAE). Disease severity was evaluated at 14-day intervals, fiber quality and productivity. For the variable severity, the area under disease progress curve (AUDPC) was corrected and the percentage of control exercised by each treatment was measured. The AUDPC for target spot (C. cassiicola) was not altered with the application of treatments. For ramularia, all treatments with fungicides in its composition controlled the disease in an express way. The fiber quality was not affected by the diseases evaluated in the parameters MIC (Thickness “Fineness”), UHML (Length), STR (Resistance to Breakage), MAT (Maturation), UI (Length Uniformity) and ELG (Elongation). The conventional management with the addition of the multisite fungicide chlorothalonil provided 88.3% of productivity increase in relation to the control.