20+ Algal Leaf Spot Magnolia. Algal leaf spot begins as a round, green, somewhat fuzzy or velvety colony on the leaf surface. The key symptom of algal leaf spot is the formation of raised blotches on the leaves.
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Severely lichenized algal leaf spot.
Since algal leaf spot is most often a problem for plants that are under stress, an important step in management is to improve growing conditions. Alternaria leaf spot, angular leaf spot, anthracnose, downy mildew, powdery mildew, watermelon bacterial fruit blotch. This disease, caused by parasitic algae, is most common in the southeastern part of the united states, where it is hot and humid. Since algal leaf spot is most often a problem for plants that are under stress, an important step in management is to improve growing conditions.