ANÁLISE COMPARATIVA DE CURVAS DE PROGRESSO DE DOENÇAS FOLIARES DA SOJA (Glycine max) TRATADAS COM COMBINAÇÕES DE FUNGICIDAS

Abstract

Annually, due to environmental differentiation in Brazil, soybean crop diseases infect differently, causing losses of different magnitudes. The objective of this work was to make a comparative analysis of progress curves of soybean foliar diseases treated with combinations of fungicides. The experiment was conducted at the Cerrado Consultoria Experimental Station, located at Agropecuária Vale Verde, Unaí, MG. The soybean cultivar used was DM 73i75, population of 260 thousand plants per ha and 0.50 m spacing between rows. The experimental design used was randomized blocks (DBC), with 16 treatments and four replications. The plots were composed of five rows of six meters each, totaling 15 m² of total area per plot. For harvesting, the two central lines were used, disregarding 0.5 meters from the ends. Treatment applications were carried out with the aid of a CO2 pressurized backpack sprayer, with a pressure of 4.5 kgf cm-², displacement speed of 1.0 m s-1, making a spray volume of 150 L ha-1. Four applications were carried out at different phenological stages, namely V6, R1, R1+15 days, R1+30 days, respectively. From 16 treatments (15 treatments plus the control) the severity was evaluated during stages R1 to R6 for six fungal diseases represented by anthracnose (Colletotrichum truncatum), septoria (Septoria glycines), cercosporiosis (Cercospora sojina), target spot (Corynespora cassiicola), Asian soybean rust (Phakopsora pachyrhizi) and powdery mildew (Erysiphe diffusa), allowing the construction of disease progress curves. The most effective treatments in temporally reducing the severity of frogeye spot and brown spot were T5, T7, T8 and T10. In the case of the target spot, it presented a lower average area under the disease progress curve (AACPD) in the T5 treatment. Anthracnose was less severe in treatments T2, T5, T7, T9, T11 and T13. The severity of Asian rust was lower in treatments T5, T7, T9. Powdery mildew severity was lower in treatments T5, T7, T9, T11 and T13. It is concluded from this work that different combinations of fungicides are effective in control, however treatments T5 (five times) and T7 (four times) were more effective.