Optimal control analysis of coffee berry borer infestation in the presence of farmer's awareness

Coffee is the most critical stimulant beverage in the world and represents a significant source of income in many tropical and subtropical countries. In this paper, a deterministic mathematical model has been formulated to describe the infestation dynamic of coffee berry borer (CBB) using a system of non-linear ordinary differential equations with farmers' awareness and optimal control. The system has two equilibrium points, namely the CBB free equilibrium point and the endemic equilibrium point which exist conditionally. The basic reproduction number, which plays a vital role in mathematical epidemiology, was derived. The qualitative analysis of the model revealed the scenario for both CBB free equilibrium and endemic equilibrium points. The local stability of the equilibria is established via the Jacobian matrix and Routh-Hurwitz criteria, while the global stability of the equilibria is proven by using an appropriate Lyapunov function. The normalized sensitivity analysis has also been performed to observe the impact of different parameters on the basic reproduction number. We extended the proposed model into an optimal control problem by incorporating two control variables, the effort made to reduce the colonizing females based on chemicals, traps, and biological control using entomopathogenic fungi such as Beauveria bassiana, that are applied to the surface of the coffee berries and kill the colonizing females of CBB when they drill an entry hole into the coffee berry and the effort made to increase the awareness of farmers through media campaign and education for the coffee farmer. Then the optimal control strategy is found by minimizing the number of CBB individuals considering the cost of implementation. The existence of optimal controls is examined using Pontryagin's minimum principle. Finally, the numerical simulations show agreement with the analytical results.