The persimmon tree, whether American (Diospyros virginiana) or Asian (Diospyros kaki), is generally hardy. Black spots on the foliage signal stress or the presence of a pathogen. This discoloration is the tree’s physical reaction to an irritant, and determining the exact cause is the first step toward restoring health. These symptoms usually result from a biological infection or an environmental problem.
Fungal Leaf Spot Diseases
The most frequent cause of black spots is a fungal infection, often called leaf spot disease. Pathogens such as Pseudocercospora diospyricola initiate the disease cycle during wet conditions in spring and early summer. The resulting spots typically appear as small, dark brown or black lesions that are frequently angular, limited by the leaf’s vascular veins. As the infection progresses, these lesions may coalesce into larger, irregular blotches, sometimes surrounded by a lighter halo.
Another common fungal issue is Anthracnose, caused by fungi like Colletotrichum gloeosporioides, which thrives in warm, humid conditions. Anthracnose spots are characteristically dark, sunken lesions that can affect the leaves, leaf stalks, twigs, and fruit. Severe infections cause leaves to turn yellow and drop prematurely, often leading to significant defoliation by late summer. This early loss of foliage hinders the tree’s ability to produce sugars, weakening the tree, reducing fruit quality, and impacting energy storage for the following season.
Environmental and Pest-Related Causes
Black spots not caused by fungal pathogens often stem from environmental factors or minor pest activity. One cause is manganese toxicity, a disorder occurring in highly acidic soils where the pH falls below 6.5. This excess uptake of manganese manifests as small, dark spots concentrated on the leaf surface, often accompanied by an irregular, pale yellow margin. These symptoms are distinct from fungal spots and signal a nutrient imbalance in the soil.
Chemical burn or phytotoxicity can also create black lesions on leaves, typically resulting from misapplied fertilizers, contaminated water, or herbicide drift. Chemical spots may appear as near-perfect circles with a bleached center or as browning along the leaf margins. Unlike a spreading disease, chemical burn damage usually affects only the leaves exposed at the time of application and does not progress. A sooty black coating on the leaves indicates sooty mold, a fungus that grows on the sticky “honeydew” residue excreted by sap-feeding pests like aphids or scale.
Identifying the Specific Cause
A systematic inspection of the tree is necessary to distinguish between the causes. Begin by noting the location and shape of the spots; fungal leaf spot often presents as angular lesions limited by leaf veins, while chemical injury may produce more uniform, circular shapes. Check the texture of the spots, as fungal Anthracnose can cause distinctly sunken lesions on the leaf stalk. Sooty mold, conversely, presents as a non-penetrating surface film that is easily rubbed off.
Observe which leaves are affected first; older, lower leaves are often the initial target of fungal diseases and some nutrient deficiencies. Sunscald damage is more likely to affect the most exposed leaves at the top of the canopy, manifesting as large, scorched, light-colored areas that can turn black as the tissue dies. Look for secondary signs, such as a sticky residue or the presence of ants, which suggest a pest problem, or an overall yellowing of the leaf, which points to a nutrient issue.
Management and Long-Term Tree Health
Managing black spots begins with cultural practices that reduce favorable conditions for pathogens and pests. Sanitation is paramount: fallen leaves and infected debris should be raked up and disposed of immediately, as fungal spores can overwinter in this material. Prune the canopy to improve air circulation, which helps foliage dry faster and discourages the moist environment fungi require to thrive.
Proper watering techniques are also important; always water the tree at the base near the drip line and avoid overhead irrigation, which wets the leaves and assists spore spread. For confirmed fungal infections, a protective fungicide application may be used, timed for spring during the full bloom stage and again three to four weeks later. If a nutrient issue is suspected, such as manganese toxicity, a soil test should be performed, and the soil pH can be adjusted upward using lime or dolomite.