Spatial weed distribution and economic thresholds for weed control.

Abstract Declining real cereal prices, increased input costs and increased awareness of the environment are likely to necessitate making spraying decisions on the basis of economic thresholds. In order to increase its utility, the threshold model can be adapted to consider the spatial distribution of weeds in a field. Results of computer simulations show that spatial distribution can have a substantial effect on calculated thresholds, relative to the effect of variation in distributions of weeds within patches. The results of a preliminary investigation into the use of aerial surveillance techniques to estimate weed-patch areas are presented, and the need for further experimental and theoretical work is underlined.