Effect of fungicide application times in the control management of leaf foliar diseases in maize

This study aimed to evaluate the effect of fungicide trifloxystrobin (200 g/L 20% m/v) + tebuconazole (100 g/L 10% m/v) at different phenological stages in controlling southern rust and Cercospora leaf spot in the maize crop and on its productivity. This work was carried out in 2013, Ertel farm, located in the city of Toledo – PR of Brasil. The experimental design was a randomized complete block in a factorial (2x4+1) with four replications. The treatments consisted of evaluating two diseases, Southern Rust and Cercospora leaf spot, and four phenological stages of fungicide application (V8, V10, VT and R1 of maize) with the presence of a control. The authors evaluated the disease incidence and severity, the Area Under Disease Progress Curve (AUDPC) and the fungicide control efficiency for foliar diseases were observed. In addition to this, some agronomic variables were also evaluated: plant height, ear insertion height, stem diameter, average diameter of ear, ear length, number of rows per ear, number of grains per row, number of grains per ear, thousand grain weight and productivity. The results showed no significant statistical difference for the variables evaluated, except for plant height. Based on these results, it can be concluded that the mixture of triazole with estrobirulina is feasible to control the severity of these diseases in maize, though it was not observed any statistical difference in the different treatments in relation to the average productivity. It is worth mentioning that the use of fungicide tends to provide greater sanity to plants and consequently it improves production rates. In general, the application of the fungicide in the pre-anthesis stage (VT) tends to exhibit better responses.   Key words: Zea mays L., Puccinia polysora, Cercospora zeae-maydis.