Powdery Mildew (fungus – Erysiphe taurica): Infected leaves are covered with a white powdery material. When disease is severe, infected leaves can be distorted. Benomyl can be used for the control of this organism, however, control is not generally necessary.
Spongy Yellow Heart Rot (fungus – Fomes everhartii): The fungus enters through broken limbs or through insect tunneling. In advance stages the interior of the tree will be a soft, spongy yellow or brown mass. Perennial cankers are bracket to hoof shaped. The upper surface of the fungus is dark brown to black while the underneath is a dull reddish brown. Control is not recommended.
Rust (fungi – Ravenelia arizonica and Ravenelia holwayii): Rust attacks the leaves causing a distortion of the leaf mid vein. It is most often observed on the first leaves in the spring. Damage is usually not significant and control is not required.
Leaf Spot (fungus – Cercospora prosopidis): Although the fungicide benomyl would control the leafspot, its use is generally not necessary due to the limited damage caused by the fungus.
Crown Gall (bacterium – Agrobacterium tumefaciens): (See section on Crown Gall)
Cotton Root Rot (fungus – Phymatotrichum omnivorum): (See section on Cotton Root Rot)