This paper describes a dynamic simulation model that allows for comprehensive assessment of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus‐galli complex) in Philippine rice farming systems. The main outputs of the model include weed seed and plant densities and seasonal and annualised profit over the simulated planning horizon. Results broadly indicate that a mixture of chemical and non‐chemical treatments provides good weed control in rice crops, and maximises long‐term profit for systems where the main weed is annual barnyardgrass. However, the performance of this strategy is heavily influenced by crop establishment method and labour cost. At current labour cost and low weed density, the regular use of manual weeding is the most valuable primary form of weed control in rice farming systems, relative to herbicide application. Herbicide application becomes more profitable than manual weeding when labour costs increase or the population of barnyardgrass plants is not maintained at its optimal level. These results illustrate the value of the model for guiding the efficient control of annual barnyardgrass in rice crops in the Philippines.
