The potential role of weed functional groups in cropping systems

摘要

Many farmers adopt integrated weed management (IWM) only when forced to by herbicide resistance, probably because of short-term costs and difficulties in management. Furthermore, while IWM packages address individual weed species, paddocks usually have a range of species and it is difficult for growers to determine the optimal management for all species present. Suppression of one or two species will often lead to an increase in the others with little or no effect on the overall weed burden. Can thecosts of weeds be reduced, and the ease of management increased, by developing control tactics for 'functional' groups of weeds rather than individual species? Weed species could be placed in 'functional' groups according to their a) biological characteristics (e.g. seed dormancy or shattering), b) phenological development (emergence, early growth, flowering and seed development), and/or c) responses to management, including herbicides, tillage, or associated crop/pasture species. By placing weeds in groups, a number of windows of opportunity could be developed, for example, by tailoring optimal herbicide mixtures, early or late timings of herbicide application, and time of cutting in pastures or forages. Such an approach would place less selection pressure on individual weed species and help to minimise herbicide resistance development however it may result in shifts in dominance to difficult-to-control species. The prediction of spread and changes of abundance of species may also be improved. In this paper we consider whether weed functional groups can be defined in a way that may lead to improved weed management in cropping systems.