Using a simple lattice model describing infectious tree disease dynamics on a homogeneous landscape we can observe an Epiphytotic phase transition from local confinement of the pathogen to a global epidemic through the forest. The phase transition can be understood in terms of the forest tree density and the pathogen virulence. One interesting application of the model involves capturing the pathogen spread-velocity and applying simple statics to pre-empt the phase transition into the Epiphytotic regime. Theoretically this yields an early warning system. The early warning phase transition could potentially be utilised to inform control strategies and negate system wide devastation of plant species.