Indian Hawthorn Leaf Spots

Source and Spread

• The culprit behind Indian hawthorn’s disfiguring leaf spots is a fungal pathogen called Entomosporium maculatum. This fungus infects plants typically during periods of cool, wet weather, because it requires water to reproduce. The fungal fruiting bodies release their spores, which land on the host plant’s leaves and shoots and splash onto nearby plants, spreading the disease. The wind can also disperse the spores. The fungus lives on dropped leaves and debris under the plants, where it continues to grow until splashing water or gusting wind catapults it back onto shrubs, perpetuating its life cycle.

Symptoms and Damage

• Characteristic entomosporium leaf spots begin as small red dots on the leaves. As the fungus grows, the dots enlarge and develop gray centers. Progressively, the dots may coalesce and take irregular shapes. Infected leaves fall from the plants, sometimes so heavily that little foliage is left clinging to the stems. Premature leaf drop weakens plants because they are unable to perform photosynthesis. If a plant is unable to produce new leaves quickly enough, it may die.

Prevention

• Prevention offers the surest way of controlling Indian hawthorn entomosporium leaf spot. If you have not planted these shrubs in your garden yet, selecting cultivars that have been bred for resistance to the disease is your best first step. “Eleanor Taber,” which has pink flowers, “Georgia Petite,” a shorter selection with white flowers, and “Indian Princess,” which has flowers that open pink and fade to white, have leaf-spot resistant foliage. If you've already planted non-resistant Indian hawthorns in your garden, you may be able to manage the onset of leaf spot disease by redirecting sprinklers away from the shrubs and watering with drip irrigation instead.

Control

• Fungicides may help prevent entomosporium disease, although they will not cure infected plants. If your plants had leaf spots last year, apply a fungicide to protect next season’s new growth. As new leaves begin to grow, spray the plants with a pre-mixed fungicide that contains chlorothalonil, copper hydroxide or thiophanate-methyl, particularly during cool, wet spring weather. Thorough coverage of all plant parts is important. Before spraying, rake all fallen leaves underneath the plants to remove all sources of the disease. Follow the label directions because you may need to continue spraying at two-week intervals during wet weather.