The short-run effects of fungicide application on economic risk and the effects of risk on fungicide use in Swiss wheat production are empirically explored. A quadratic production function model is developed. With the help of the moment-based approach, marginal contributions of fungicides (representing controlled inputs) and of rain (representing uncontrolled inputs) to the variances of yield and revenue are analyzed. It is not possible to show risk-reducing effects of fungicides on yield or revenue. At low rain quantities during the vegetation period fungicides have a statistically significant risk-increasing effect on revenue. Increasing risk leads Swiss wheat growers to use more fungicide. This increase is statistically significant at higher levels of revenue. For example, when risk is doubled fungicide inputs are raised by 44% at the highest revenue quartile.