The infection that is being seen now occurred in February or early March when the tiny peach or nectarine buds began to grow. The symptoms of this disease are curled, thickened often red or purplish colored leaves. Later these leaves will develop a white to grayish bloom. This bloom is the production of fungal spores that move in wind and rain to the bark of your trees and other trees nearby. The spores on the bark do no harm to the trees till the following spring when the cycle is repeated.
Peach Leaf Curl is often called a cosmetic disease – infected leaves bothers gardeners more than the trees. Severe infections can weaken the tree reducing growth and future crop potential. This disease usually infects leaves, rarely flowers, fruit and twigs. Infected flowers and small fruit may drop without being noticed
Once the infection is visible, it cannot be cured this year. It can be easily prevented for next year. To prevent it you can apply an organic fungicide (Lime Sulfur or Fixed Copper) in late winter (February) and maybe in the fall, or, you can grow your trees under the eve of a building or a free standing rain cover for February and March.
For more information see the BC Ministry of Agriculture PDF about Peach Leaf Curl