Antifungal Treatment for Ornamental Apple Trees

About Ornamental Crabapples

• Ornamental apples are those grown more for their attractive flowers than for the fruit, though the small red crabapples are ornamental as well. Some varieties have purple leaves or vibrant fall color, some are small and spreading while others are tall and open. Flower color ranges from white to pink to deep rose. Susceptibility to disease also varies and planting resistant varieties is your best defense against disease. Crabapples are fairly drought tolerant but be sure to water well during the first few years to establish a deep root system.

About Fungus Diseases

• Fungi cause a wide variety of apple diseases including scab, powdery mildew, fruit rot, rust, sooty blotch and fly speck. The life cycle of the fungus that causes each of these is slightly different from the others. For instance, apple scab overwinters in diseased leaves on the ground and produces spores that infect the apple trees in early spring. Powdery mildew, on the other hand, overwinters in fruit or leaf buds on the tree and then infects the new shoots as they develop.

Treatments

• The most effective way to prevent disease is to plant only crabapples that are resistant to the common diseases in your area. If you already have a crabapple that has shown symptoms, apply a fungicide during dormancy to prevent the first cycle of infection. Some common fungicides are thiophanate-methyl, basic copper sulfate, lime sulfur, wettable sulfur, bordeaux mixture (copper sulfate and lime) and captan. Choosing among these requires identifying the disease. Ask your local extension service for advice.

Resistant Varieties

• Some crabapple varieties that are resistant to most common fungal disease are Centurion, an upright variety with rose-red flowers; Coralburst, with semi-double rose pink flowers; Louisa, a weeping variety with pink flowers and yellow fruit; Prairiefire, red flowers and orange-red fall color; Robinson, a 25-foot tree with deep pink flowers, and Sargent, white flowers on a small, spreading tree.