Abstract
SUMMARY: Yield responses to single applications of fungicides on winter wheat varied according to several factors of which disease incidence and spray timing were the most readily identified. In order to improve spraying decisions by farmers, judgemental distributions of yield response to spray application were specified for 16 combinations of field observations, which involved crop growth stage, disease presence, weather, cultivar susceptibility, and crop site topography. An examination of 1977 results showed that 14 out of 18 recommendations would have been correct had the scheme been in use.