Profitable management of a finite herbicide resource

A financial model of a single farm is used to analyse the profitable management of a finite herbicide supply across time. Delaying resistance can be unprofitable because of the high efficacy and low cost of herbicides, relative to alternative control methods. It is financially attractive to maintain low weed populations, independent of resistance status. Thus, the cost of resistance mainly reflects the need to use more-expensive control options. Non-selective control complements chemical use and extends the susceptibility of weeds to a finite herbicide resource. The model shows that resistance can develop as part of profitable farm management, given the high relative advantage of chemical control. Uncertainty about future herbicide availability, system complexity, temporal volatility, mitigation cost, and short land tenure are primary constraints to efficient herbicide use. This can incur significant costs, through lost profits and accelerated resistance development. •An economic model is used to analyse profitable herbicide management.•Herbicides are highly adoptable due to their high efficacy, low cost and simplicity.•Integrated Weed Management (IWM) is costly but slows resistance development.•Higher cost of IWM determines economic impact of waning chemical efficacy.•Pervasive uncertainty makes unprofitable herbicide management increasingly likely.