Modifica??o de uma barra de pulveriza??o para a aplica??o de fungicida em trigo visando ao controle de giberela

摘要

The increased frequency and yield losses in wheat, associated with head blight in Winter cereal crops in Southern Brazil, caused by the fungus Gibberella zeae, have turned this disease into a major problem. Gibberella zeae enters the host plants through the anthers. To avoid infection, the fungicides need to protect the anthers from the fungus, which requires improved spray techniques. The role of different spray nozzles (flat fan, twin flat fan, and hollow cone), different nozzles arrangements, and two spray volumes on head blight control and grain yield were evaluated. In two experiments conducted in the field, at the year 1999, the fungicidal applications reduced significantly the disease incidence, the number of infected spikelets, and disease severity. The grain yield increased as well. The spray nozzles, nozzle arrangements, and spray volumes did not influence disease control and grain yield. The differences in grain yield between treated and non-treated plots made chemical control worthy, despite its low efficacy. Fungicidal sprays to control head blight should use nozzles that deliver medium to fine droplets, at a volume of 200 L ha-1.