In rare cases of severe infection and where the size and value of plants make it practicable, applications of fungicides may be helpful. Overuse of nitrogen can cause an abundance of succulent growth.ĥ. Abundant, young, tender growth is very susceptible to attack by disease and insects. Avoid over fertilizing by testing the soil first. Since most plants can tolerate some defoliation, keep them in good health so they can rebound quickly. Pruning plants to allow for good air circulation and reducing crowding will also help keep the foliage dry.Ĥ. Watering can also spread the disease by splashing.
Use soaker hoses or water early in the day so the foliage can dry off before night. This is not a cure but may help limit infection by reducing the total amount of inoculum.ģ. Raking up and disposing of infected leaves as they drop and pruning out dead twigs can help control the disease by removing spores that can reinfect the new leaves. Only if defoliation occurs three or more years in a row will most established plants be adversely affected.Ģ. A tree affected early in the year will re-leaf and the new leaves may not be affected. Most trees tolerate leaf spots with little or no apparent damage. Overhead watering can also provide prolonged wet periods that are ideal for spreading leaf spot diseases.ġ. During wet weather, spores may splash or be windblown onto newly emerging tender leaves where they germinate in the moisture and infect the leaf. Some may remain in dead twigs on the tree. The organisms that cause leaf spots survive in fallen infected leaves and twigs. Spots or blotches that are angular are generally referred to as anthracnose (see entry on “Anthracnose of Trees”) Leaves may yellow and drop prematurely. Over time, the spots may combine or enlarge to form blotches. Fungal bodies may appear as black dots in the spots, either in rings or in a central cluster. Concentric rings or dark margins are often present. Spots are most often brownish, but may be tan or black. The spots will vary in size and color depending on the plant affected, the specific organism involved, and the stage of development. The chief symptom of a leaf spot disease is spots on foliage. Small or newly planted trees that become defoliated are more at risk of suffering damage until they become established. An established plant can tolerate almost complete defoliation if it happens late in the season or not every year. Leaf spot may result in some defoliation of a plant. Leaf spots on trees are very common and generally do not require spraying. Some insects also cause damage that appears like a leaf spot disease. The majority of leaf spots are caused by fungi, but some are caused by bacteria. Leaf spot is a common descriptive term applied to a number of diseases affecting the foliage of ornamentals and shade trees. Close-up of fungal tar spot on sugar maple ( Acer saccharum) note the characteristic ripples or wavy indentations in the black, tarry surface of the lesion