Weed and pollen mobility and social costs of herbicide resistance

摘要

Potential social costs and externalities associated with herbicide resistance have not generally been considered in economic analyses of the impact of herbicide resistance. The economics of managing herbicide resistance in weeds has focused on cost-effective responses by individual growers to the development of resistance at the individual field level, and the risk of resistance spread through weed mobility has been treated in economic analyses as if it were negligible. In reality, weed mobility needs to be assessed on a case-by-case basis. Resistance has been shown in many cases to have resulted from multiple events, rather than by spread, however, there is also a likelihood of resistance mobility through the spread of pollen, seed and plants. Furthermore, growers may perceive that they will gain resistance via mobility rather than just their own actions. In cases where weed mobility is high, failure to recognise costs associated with externalities results in myopic behaviour by individual agents,and hence overuse of the herbicide resource. In this paper we discuss the evidence for weed mobility in various farming environments, and use a simulation model to consider the impact mobility may have on the onset of resistance, weed control costs andoptimal herbicide resistance management strategies.