As a property owner, you want to keep your eyes open for a few common symptoms, such as discolored spots, powdery mildew appearing on the leaf surfaces, and leaves turning yellow out of season. Leaf spots on trees are generally not important in the scheme of things but can be unsightly.
Some spots on leaves are caused by a parasitic alga (Cephaleuros virescens). Cool wet springs are conducive to the formation of leaf spots. Three different fungi are the primary cause of spotting on leaves in trees. The majority of leaf markings are caused by fungi, but some are caused by bacteria. Bacteria leaf scorch is one of the rare tree diseases that is caused by bacteria as opposed to fungus. Bacterial blight causes brown spots (often surrounded by yellow areas) and rapid browning of young shoots. The organisms that cause spots survive in fallen infected leaves and twigs.
Sometimes, leaf scorch is misidentified as an infection problem rather than a simple watering issue. Because of the scorched appearance of the leaves, the disease is sometimes called leaf blight. Trees affected by leaf scorch can generally be treated with watering, effective fertilization, and light pruning to remove the affected leaves and branches.
The answer:
Spots on tree leaves are very common and generally do not require spraying. However, when infections are heavy, they can result in disconcerting levels of premature leaf drop and defoliation. Most trees tolerate leaf spots with little or no apparent damage. Mature leaf spots produce spores or bacteria that can be spread throughout the canopy. This can start the second set of spots or cause new infections on other plants. The later in the season that spots develop the less need for alarm.
Unless there is substantial foilage loss, there really is no cause for alarm. Contact
