Doen as foliares e o controle por fungicidas na produtividade e qualidade de gr os de trigo Foliar diseases and control by fungicides on yield and quality of wheat grains

O estudo foi estruturado no intuito de determinar os fatores, do ponto de vista do manejo químico de doen as foliares, necessários para obten o de trigo com qualidade de panifica o. O experimento em blocos ao acaso com seis repeti es buscou esclarecer a intera o entre doze cultivares e sete programas de aplica o de fungicidas e suas implica es na produtividade e qualidade de gr os de trigo. Os resultados obtidos mostraram que os efeitos proporcionados pelos fungicidas, no controle de doen as, e seus efeitos diretos na fisiologia de plantas de trigo, foram fatores determinantes para obten o de trigo com alta qualidade. Mostrando, também que as doen as comprometem a remobiliza o do nitrogênio das folhas para os gr os. Ficaram evidentes as diferen as entre estrobilurinas e triazóis no controle de manchas foliares e de ferrugem da folha, onde os fungicidas triazóis foram mais eficientes no controle do complexo de manchas foliares, quando comparados as estrobilurinas. Porém, o controle efetivo da ferrugem da folha do trigo foi proporcionado pelas estrobilurinas. Os estádios fenológicos do elongamento e emiss o de espigas s o momentos críticos para o controle químico de manchas foliares em condi es de monocultura. E a aplica o de fungicidas após o florescimento é imprescindível para o adequado manejo da ferrugem da folha. The study was structured to determine the necessary factors, from the point of view of chemical control of foliar diseases, to obtain high quality wheat for bread production. The experiment in randomized blocks with six replicates tried to clarify the interaction between twelve cultivars and seven fungicide application programs, as well as its implications in the yield and quality of wheat grains. The results showed that the effects provided by fungicides in disease control, and their direct effects on the physiology of wheat plants, were decisive factors for obtaining high-quality wheat. The results also showed that diseases compromise the remobilization of nitrogen from leaves to grains. The differences between strobilurins and triazoles were evident in the control of leaf spot and leaf rust, in which triazole fungicides were more effective in controlling the leaf spot complex, when compared to strobilurins. However, effective control of wheat leaf rust was provided by strobilurins. The phenological stages of elongation and emission of spikes are critical times for the chemical control of leaf spot under conditions of monoculture. In addition, the fungicide application after flowering is essential for the appropriate management o