Effects of different conditions of irrigation and crop density on microclimate and occurrence of spot blotch and powdery mildew.
Field experiments were carried out in Campinas, São Paulo, Brazil, during the winter seasons of 1990 and 1991 to study the effects of sprinkler irrigation and crop density on micrometeorological parameters (av. air temp. and dew duration) and evaluate their influence on the occurrence of spot blotch (Helminthosporium sativum [Cochliobolus sativus]) and powdery mildew (Erysiphe graminis) on wheat. The results obtained were submitted to statistical analysis (comparison of means of 2 independent sample analysis (microclimate) and confidence interval analysis (infection rates)). Evidence was obtained that in the densest and the most irrigated plots the av. air temp. were lower (0.7°C) and the dew durations (DPM) were longer (45 min) than in the other plots. The infection rates were increased by irrigation and high crop density when macroclimatic conditions were not favourable to disease development.