The disease causes circular spots with necrotic centers and a black border, and usually occurs during cooler weather conditions.
A close up of the infected leaf will indicate cracking inside the necrotic region.
Wind and water movement aids in spread of the fungal spores of the pathogen from a few infected leaves or plant debris.

Fungal causal agent: Pestalotiopsis sp.

PESTALOTIOPSIS BLIGHT

Magnolia diseases