Fungus is a common problem with many fruit and nut trees, and pecans are no exception. With more than 10 common microorganism types, diseased pecan trees are a common sight. Thankfully, very few trees will actually die from fungal infections.
Tree fungus damages the foliage and nuts on pecan trees. Some of the most common symptoms include infected nuts falling from the tree prematurely, white powdery growth on the leaves and swollen tumors on the tree's limbs, resulting in a tree lacking in vigor.
Typical types of tree fungus include scab, powdery mildew, blotch, heart rot, rosette and crown gall. Certain fungal infections are more common in certain areas of the United States. For example, downy spot (Mycosphaerella caryigena) is cost commonly seen in Arkansas pecan trees in late June or early July.
Most fungi occur during the last summer, when the conditions are the most humid. To prevent infections from occurring and spreading, anti-fungal treatments should be applied regularly throughout the growing season. For recommended local treatments, contact your county extension office.
Each fungus has different symptoms, but in general anything that does not look normal on a tree is most likely an infection. For example, pecan scab (Cladosporium caryigenum) causes black spots on the leaves and stems of the tree and the nuts will fall off the tree early. Powdery mildew (Microsphaeria alni) creates an unattractive white powdery growth on the tree's leaves but will not actually harm the nuts.
Most fungal infections will not kill the tree. Some fungus such as pecan scab (Cladosporium caryigenum) and internal breakdown (unknown fungus) will directly affect nut production. Diseases such as crown gall and downy spot (Mycosphaerella caryigena) affect the foliage and the tree's overall growth.