Economic analysis of weed management options in rice production in the Philippines

[Truncated abstract] The use of herbicides in Philippine rice production is rapidly increasing, particularly in areas where rice crops are direct-seeded instead of transplanted. Manual weeding and flooding were traditionally used to restrict weed competition with crops, but their cost is increasing due to an increasing labour costs and limited water supply. However, the use of herbicides has been accompanied globally by the potential build up of herbicideresistant weeds, weed species population shifts, and concerns about environmental contamination and impacts on human health. Rice farmers have generally been encouraged to use integrated weed management (IWM) strategies by PhilRice, the organisation responsible for enhancing the country’s rice productivity through research and development, to avoid high herbicide use, while still attaining good yields. These IWM strategies have benefits for the control of rice weeds by delaying the development of resistance or allowing the control of herbicideresistant weeds. Nevertheless, the inherent complexity of decision-making in terms of weighing the relative benefits and costs of IWM control options makes the identification of advantageous strategies problematic. Key factors are the broad range of information that requires consideration in an integrated manner, the large number of alternative treatments and their possible combinations requiring evaluation, and their interrelationships with other components of the farming system. The primary objective of this study was to develop a bioeconomic model to comprehensively analyse the implications of IWM strategies for rice production in the Philippines. The model, Resistance and Integrated Management in the Philippines (RIMPhil), was designed to address the effective management of annual barnyardgrass (Echinochloa crus-galli complex), one of the major rice weeds in this nation. The model was used to investigate a number of weed management issues over a twentyyear period.