Phytophthora species are microscopic organisms that harm plants. Multiple Phytophthora species can infect madrones and cause root rot. Learn more about this disease on our Phytophthora webpage.

Landowners can suspect Phytophthora root rot if a wilting tree does not respond to increased watering and the spores actually move through water in the soil.

Many fungi have been identified in association with foliar disease symptoms on madrone, but their roles and threats are poorly understood. Some of them cause severe leaf blight and also infect shoots, causing shoot dieback. Others cause minor symptoms.

Different fungi predominate in different years depending on the climate conditions. Some of the fungi colonize the fruits, which may affect regeneration from seed and also food supplies for wildlife.

See our Foliar Blight webpage for more information.

Cankers are fungal infections on woody tissue.

On madrone, the sunken cankers with irregular, black margins on stems and branches are caused by the fungus Neofusicoccum arbuti. They are often centered on a branch stub or an injured area.