Symptoms: A fungal disease that affects peaches and nectarines, leaf curl (Taphrina deformans) is one of the most common disease problems found in backyard orchards. It appears in spring as reddish areas on developing leaves. These areas become thickened and puckered, causing leaves to curl and distort. When severe, leaf curl can substantially reduce fruit production.
Disease fungi overwinter as spores (conidia) underneath bark, around buds and in other protected areas. Early in the growing season, during cool, wet spring weather, the spores infect new leaves as they emerge from the buds. Later, the fungus produces great numbers of new spores which are splashed or blown from tree to tree.
Leaf curl is most active at temperatures between 50 and 70 degrees F. Because the disease can occur at relatively low temperatures, cool weather is thought to extend the infection period because the new leaves are growing slowly. Wet weather is necessary for infection.
Control: Select resistant varieties whenever possible. Leaf curl can be controlled by applying sulfur or copper fungicides. Spray the entire tree after 90% of the leaves have dropped in the fall, and again in the early spring, just before the buds open. Keep the ground beneath the trees raked up and clean, especially during the winter months. Prune and destroy infected plant parts as they appear. If leaf curl is severe, growers must maintain tree health and vigor by cutting back more fruit than normal, watering regularly (avoiding wetting the leaves if possible) and applying extra nitrogen fertilizer.
Photo Credit: Michigan State University