Development and evaluation of a multiple-pest, production situation specific model to simulate yield losses of rice in tropical Asia

A yield loss simulation model for rice was developed to simulate injury mechanisms due to pathogens, insects, and weeds, and the yield losses they cause in a range of production situations. The structure of the model is simple, flexible, and involves as few parameters as possible. The model consists of two linked components. The first simulates the dynamics of the rice crop, with accumulation of biomass and its daily partitioning towards leaves, stems, roots, and panicles. The second component simulates the dynamics of tillering, tiller maturation, panicle formation, and tiller death. Coupling functions representing damage mechanisms due to sheath blight, stem borers, and weeds were developed and parameterized from published and experimental data. Each of these injuries corresponds to a set of damage mechanisms, some of which are specific to the injury considered, while others are common to several injuries. The parameters required to simulate attainable growth and attainable yield were determined, using specific field experiments, under three different production situations representing those commonly occurring in the Philippines and in Vietnam. Yield loss simulations due to the different injuries, considered alone or in combination, were tested under these different production situations. The model accurately simulated attainable rice growth and development, and adequately accounted for the yield-reducing effects of the different injury mechanisms considered. Results from sensitivity analyses conducted at varying levels of injuries are discussed. This model can be used as a tool to set research priorities for novel plant protection strategies for rice in tropical Asia.