Peach leaf curl
Leaves pucker and take on a slight reddish tinge. A powdery white film later develops over the affected leaves. This generally happens as soon as the new foliage unfurls in the spring.
A fungus. The spores are carried by wind and rain landing and lodging in cracks and crevices of the tree and overwintering there, ready to leap into action the following spring.
Generally the health of the plant is not effected unless the infection continues year after year. Less fruit might be produced. The skins of nectarines may also be come rough as the fungus spreads to the fruit. Peaches are not similarly affected.
Organic - grow trees in a greenhouse where the spores are unable to reach them. Outdoor trees can be protected with a polythene canopy which provides shelter from the rain and prevents the spores spreading. The cover must be in place from mid-winter until late-spring. Also, remove infected leaves once spotted. Feed and water the tree well so that new leaves are encouraged, these new leaves tend to remain unaffected.
Chemical - spray with fungicide between mid- to late winter. You must stop spraying once the buds start to open.