Peach Leaf Curl is a common fungal disease that affects peach and nectarine trees. The condition is caused by the fungus Taphrina deformans, which infects the developing leaves as they emerge from the bud in spring. The fungus survives the dormant period on the tree itself, requiring a preventative approach for effective control.
Recognizing the Symptoms
The first signs of Peach Leaf Curl appear shortly after the buds break in the spring. Young leaves show characteristic distortion, becoming thickened, puckered, or blistered. These affected areas often display coloration ranging from red, pink, or purple hues.
As the infection progresses, the thickened leaf areas may turn yellowish before acquiring a grayish-white, velvety coating. This coating is a mass of fungal spores (ascospores) that are released and spread. Severely infected leaves eventually turn yellow or brown and drop prematurely, sometimes causing significant early defoliation. The fungus can also infect young shoots and fruit, causing them to become stunted, distorted, or develop reddish, raised patches.
Immediate Action for Infected Trees
Once curled leaves are observed in spring, chemical treatments are no longer effective because the fungus is already inside the leaf tissue. The focus shifts to supporting the tree’s health so it can produce a healthy second flush of foliage. This new growth, which develops when conditions are warmer and drier, is typically not reinfected.
Gently remove any severely infected leaves within easy reach and dispose of them promptly. Proper sanitation is important, so rake up and destroy any fallen leaves or fruit that might harbor spores. To help the tree recover from defoliation, maintain consistent soil moisture through regular watering and apply a balanced fertilizer, particularly one containing nitrogen, by mid-June. These practices reduce stress, allowing the tree to generate new, healthy leaves for the remainder of the growing season.
Essential Dormant Season Prevention
Control of Peach Leaf Curl relies on preventative treatments applied during the dormant season. The Taphrina deformans fungus overwinters as spores lodged in the bark crevices and on the bud scales. When cool, wet conditions coincide with bud swell in late winter or early spring, water washes the spores into the newly opening buds, causing infection.
The ideal time for treatment is in the late fall, after 90% of the leaves have dropped, and then again in late winter before the buds begin to swell. This timing is crucial because the fungicide must coat the dormant twigs and buds to kill overwintering spores before they enter the emerging leaf tissue. In regions with high rainfall or extended cool, wet springs, a second or even third application may be necessary, sometimes around New Year’s and again around Valentine’s Day.
Fixed copper fungicides, such as Bordeaux mixture or copper soap (copper octanoate), are the most common and effective treatments available to home gardeners. Thorough coverage is essential, requiring the entire surface of the twigs, branches, and trunk to be sprayed until the product is dripping. Another effective option is the synthetic fungicide chlorothalonil, though its use should be alternated with copper products to prevent fungicide resistance.
Non-Chemical Management Strategies
While dormant sprays are the primary defense, several non-chemical strategies can reduce the risk and severity of infection. Selecting resistant or tolerant varieties of peach and nectarine trees is the most effective long-term approach for minimizing disease pressure.
Resistant Varieties
- ‘Frost’
- ‘Avalon Pride’
- ‘Oregon Curl Free’
- ‘Q-1-8’
The fungus thrives in prolonged wetness and cool temperatures. Growers can reduce infection by keeping the tree dry during the critical bud-swell period. This can be accomplished by training the tree under an eave or covering it with a temporary plastic rain shelter from leaf drop until mid-May, preventing rain from washing spores into the emerging buds.
Proper pruning supports tree health by increasing air circulation within the canopy, which helps foliage dry faster and discourages fungal growth. When pruning, remove any heavily infected shoots or twigs. Ensure the tree is planted in a location with good drainage and ample sunlight.