Responding to inter and intra-field variation to optimise foliar disease management wheat

The development of techniques to allow pesticide application to be spatially varied on an intra-field scale should enable a logical progression from the current practice of varying inputs according to the requirements of individual crops. The success of precision farming will depend partly on the extent to which the development of techniques to monitor crops and convert crop measurements into improved treatment decisions are guided by biological understanding of the causes of variation in input optima. Quantification of the potential benefits from spatial adjustment of fungicide treatments is currently limited by shortage of objective data on the extent of variation in representative wheat crops. There is some evidence that intra-field variation in epidemic development and the sensitivity of the crop to disease might justify spatially varied treatment, but this would require the development of complex, automated monitoring techniques. The poor relationships between past yield variation and yield variation in the current crop, and yield potential and yield response, limit the value of yield maps as tools to optimise disease control inputs.