  In this paper we propose two nonlinear models for the control of anthracnose
disease. The first is an ordinary differential equation (ODE) model which
represents the within-host evolution of the disease. The second includes
spatial diffusion of the disease in a bounded domain. We demonstrate the
well-posedness of those models by verifying the existence of solutions for
given initial conditions and positive invariance of the positive cone. By
considering a quadratic cost functional and applying a maximum principle, we
construct a feedback optimal control for the ODE model which is evaluated
through numerical simulations with the scientific software Scilab. For the
diffusion model we establish under some conditions the existence of an optimal
control with respect to a generalized version of the cost functional mentioned
above. We also provide a characterization for this optimal control.
