3 tab. Sum. (De, En)

A method was developed to quantify the rate of coffee rust development. The method involved assessment of rust intensity of individually mapped leaves and partial processing of this data by the computer program "LEAFAL". The rate of coffee rust development calculated based on proportion of current leaves rusted showed a false decrease due to fall of rusted leaves and due to formation of new leaves, and a false increase due to fall of not-rusted leaves. Stepwise regression identified combinations of biological and meteorological variables that explained best the variation in the rate of coffee rust development that was corrected for leaf enlargement period, incubation period, leaf fall and leaf formation. The variable, proportion of leaf area occupied by visible spore mass (spore area index) alone explained upto 78 percent of the variation in the rust development; and minimum temperature upto 72 percent depending on the prediction intervals. The above two variables along with the variables rainfall, maximum temperature and new leaves formed explained 94 percent of the variation in the rate of coffee rust development at a prediction interval of 56 days