Chiang Mai Journal of Science

The brown spot that is an important disease in rice, is found in poorly maintained soil. It is affected by the process of straw degradation or stubble. The SIX model can represent the dynamics of the disease because it includes a variable considering the number of pathogens in soil. In this work, the SIX model is advanced by adding the standard incidence rate and differentiating infection from two sources, plant and soil. The new model is then validated by using the stability analysis and the sensitivity indices of various embedded parameters. The analysis illustrates that there are two equilibrium points: disease-free and endemic equilibrium. The disease-free equilibrium is asymptotically stable when R₀ <1 . In contrast, the endemic equilibrium is asymptotically stable when  R₀ >1 . In addition, the analytical results were confirmed by numerical simulations of the occurrence of brown spot diseases in rice.