Peach tree curl, also known as peach leaf curl, is caused by the fungus Taphrina deformans. The disease causes foliage to produce reddish areas that thicken and pucker, causing a characteristic curling effect. Peach tree curl also affects new shoots, blossoms and fruit. In severe infections, peach tree curl can significantly reduce fruit yields. Pruning infected branches away is largely ineffective. The best treatment is a preventive fungicide that can be applied in the autumn, once the leaves have fallen. A Bordeaux mixture, made of copper sulfate and hydrated lime, is an excellent choice for this treatment.
Dissolve 1 lb. of copper sulfate in one gallon of water. Use a wooden paddle or other similar device to work the copper sulfate through the screen or sieve. Ensure that it is dissolved thoroughly.
Combine 1 lb. of hydrated lime with one gallon of water to make a suspension, in a separate plastic bucket. Set these two mixtures aside and allow them to sit for at least two hours before use.
Combine the two mixtures in a garden sprayer when ready to spray the trees. Stir the mixture thoroughly.
Seal and pressurize the sprayer. Spray the branches and trunk of the tree thoroughly, ensuring that all surfaces are evenly covered. Spray the soil surface around the tree out to the drip line.