Xanthomonas sp. causes bacterial leaf spot on magnolia. The disease is a serious issue in production during high rain and wind conditions or heavy overhead irrigation conditions which leads to easy movement of the bacteria from plant to plant.

The pathogen can enter through wounds, and stomata and hydathodes. Symptoms of bacterial infections vary but usually start as small necrotic lesions with a yellow halo region.

Under ideal environmental conditions the pathogen can severe blighting of the foliage.