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Homeowners who take pride in their properties may be alarmed to notice seemingly spotted leaves on their trees. Such spots may be indicative of a condition known as leaf spot.
In spite of its appearance, leaf spot is often harmless. According to the Missouri Botanical Garden, leaf spot is a term used to describe a number of diseases that can affect the foliage of ornamentals and shade trees. Often caused by fungi that can spread thanks to wind and/or spring rains, leaf spot also may be a byproduct of bacteria. As unsightly as leaf spot can be, the Missouri Botanical Garden advises that established plants will only be adversely affected by leaf spot if defoliation occurs three or more years in a row.
While leaf spot is often harmless, homeowners should still learn to recognize it and document its presence to ensure it does not become a long-term problem.
How to recognize leaf spot
Because leaf spot is an umbrella term that refers to various diseases, its symptoms can vary depending on which type of leaf spot is affecting a tree.
• Spots: The spots of leaf spot vary in size and color depending on the plant, the organism that's affecting it and the stage of development. Spots are typically brown, but can be tan or black as well.
• Margins: Another sign of leaf spot is the presence of concentric rings or dark margins on the leaves around the infected areas.
• Black dots: If fungus is the cause of the leaf spot, the fungal bodies may appear as black dots in the spots. These dots may be within the rings or in central clusters.
• Yellow leaves: Some leaves that are infected with leaf spot turn yellow and drop prematurely.
If leaf spots are not noticed immediately, they may gradually combine to form large blotches.
How to address leaf spot
Leaf spot does not necessarily need to be addressed. As the Missouri Botanical Garden notes, many trees tolerate leaf spot and suffer little to no damage. In addition, the University of Minnesota Extension notes that the majority of leaf spot diseases affect only a small percentage of infected trees' overall leaf area and are only minimal stressors on the trees.
But homeowners who want to address leaf spot can take certain steps to do so.
• Remove infected leaves. As infected leaves fall, homeowners can remove them so the spores that caused the initial infection cannot be blown onto healthy leaves and spread the disease.
• Remove dead twigs. Removing dead twigs also can help get rid of spores that can contribute to infection.
• Change watering techniques. When watering trees, homeowners who want to prevent leaf spot or stop it from spreading can avoid overhead watering, instead using soaker hoses. Watering early in the day also can give foliage ample time to dry off before nightfall.
• Prune plants. Pruning plants promotes healthy air circulation and reduces crowding, which can help keep foliage dry, making trees less vulnerable to leaf spot.
As unsightly as it can appear, leaf spot is often harmless. But homeowners can take steps to prevent it and stop it from spreading to healthy leaves.