Phakopsora pachyrhizi Sydow & Sydow is the worst threat for soybean crop in the most important growing regions around the world, where great losses were observed. Many variables are studied in the quantification of damage such as area under the disease progress curve (AUDPC), healthy leaf area absorption (HAA), healthy leaf area duration (HAD), in addition to disease progress curves. The present research aimed to evaluate the effect of several herbicides and fungicides on the progress of the disease and its implications for variables related to healthy leaf area and yield. The treatments were evaluated in two cultivars (MG/BR-46 Conquista e BRS Valiosa RR): 1. Control; 2. Control with herbicides; 3. Herbicides and pyraclostrobin (V4) + pyraclostrobin+ epoxiconazole (R2 and R5.1), 4. Herbicides and pyraclostrobin (V4) + epoxiconazole (R2 and R5.1). 5. Herbicides (V4) + pyraclostrobin + epoxiconazole (R2 and R5.1). The herbicides used in MG/BR-46 Conquista were sethoxydim, bentazon and chlorimuron-ethyl; in BRS Valiosa RR, glyphosate was used. The logistic was the model that best adapted to the mean severity ratings and the disease progress curve. At the bottom of canopy, position more favorable to this disease, the logistic model with variable rate was the model that better explain the data. The spraying of strobilurin's group associated with triazole (pyraclostrobin + epoxiconazole) reduced the rate of asian rust development, in relation to the group of ergosterol biosynthesis inhibitors fungicide (epoxiconazole). The pyraclostrobin + epoxiconazole influenced the variables AUDPC, HAA and HAD, and these can be considered suitable to quantify damage caused by this disease. In MG/BR-46 Conquista, the herbicides action affects temporarily the leaf area, affecting indirectly the HAA and HAD variables.
Glycine max (L.) Merrill; AUDPC; HAA; HAD; strobilurin; triazole
