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Peach Leaf Curl (Taphrina deformans)
The first indication of this fungal disease is puckered and curled leaves.
The leaves begin a pale green but develop a deep pink to purple colour. A white bloom will appear on the surface of the leaf, and then the leaf dies and falls off.
Infected fruit will be stunted and puckered and will usually fall off too.
New leaves will grow to replace the lost ones, but continual attack by the disease will weaken the tree.
On apricot trees whole shoots are affected, so that the curled leaves grow abnormally close together in a bunch.
Disease Cycle
Cool, wet conditions during leaf emergence in spring favour the development of leaf curl. The disease is stopped by high summer temperatures and the fungus survives summer as ascospores. These germinate in autumn rains and form yeast-like spores that can overwinter in bud-scales and on twigs. These spores then infect the newly developing leaves that are produced from such buds in spring.
Control
The leaves are infected when they are bursting from the buds, so by the time the symptoms are noticed any control measures for that year are useless.
Timing is the key to control of this disease. One application of copper oxychloride or copper hydroxide is usually sufficient to control it but it must be done at or just before early bud-swell (as the buds are beginning to get plump).
Where the disease has been difficult to control in previous seasons, a program of three sprays is recommended. The first spray should be applied in autumn, at leaf fall. The second spray should be applied immediately before budswell at the late dormant stage, and the third spray about one week later at budswell.
Do not apply after the buds have burst as it is too late to control the disease and young leaves will be burned.
The Chemicals
Copper oxychloride is a low toxic, broad spectrum chemical fungicide. It is effective against brown rot, anthracnose, black spot, downy mildew.
It is allowable under NASAA organic standards but copper hydroxide preferred.
Copper hydroxide (Bordeaux mixture, Kocide, Champion) is made by combining copper sulphate with hydrated lime. It is allowable under NASAA organic standards.
Information sourced from:
What Garden Pest or Disease is That? By Judy McMaugh, New Holland publishers
Department of Primary Industries Vic, www.dpi.vic.gov.au
Photograph courtesy of Heyne's Garden Centre: www.heyne.com.au
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