Thresholds for control of Septoria spp. in winter wheat based on precipitation and growth stage

A simple forecasting model for Septoria spp. in winter wheat was developed based on historical data (1980–89) including precipitation, growth stage, disease severity and yield response to fungicide treatments. The number of days with precipitation ≥ 1 mm, calculated during a 30‐day period starting at the beginning of stem elongation (GS 32), correlated well with attacks of Septoria spp. later in the season and with the yield response in trials with fungicide treatments. Seven or 8 days with rainfall ≥ 1 mm was suggested as a threshold for Septoria treatment. Model development and possible further improvements are discussed.