Threshold Relative Humidity Duration Forecasts for Plant Disease Prediction

Abstract

Duration of high RH periods is an important component of many plant disease development models. Performance of forecasts of this quantity, based on the model output statistics 3-h temp. and dewpoint forecasts produced by the National Meteorological Center, USA, is examined for selected locations. A probability model for high RH duration conditional on these forecasts is presented, which describes forecast performance and would be straightforward to use. The forecast humidity duration intervals are relatively broad, but their transformation into probability forecasts of disease severity ratings, illustrated for the case of potato late blight [Phytophthora infestans], produced good results