Other
Peach Leaf Curl
Taphrina deformans
Fungus
In a Nutshell
- Leaf deformation and reddish discolouration.
- Fungal growth on leaves.
- Premature defoliation.
Can also be found in
Other
Symptoms
Symptoms usually appear soon after a leaf burst. Leaves become thickened and severely distorted with a puckered, crumpled or curled limb and a reddish to purple discolouration, depending on the variety of tree. As the infection progresses, the affected leaves take on a whitish-grey, powdery appearance due to the development of a fungal bloom on their surface. The grey covering gradually turns black, a process that coincides with higher daytime temperatures. Eventually, the diseased leaves die and fall, leading to defoliation and loss of vigour. They are soon replaced by new leaves emerging from the same growing point. Areas of bark or whole shoots can also be blackened when the infection becomes systemic, during which the fungus will start to spread within the plant's internal tissues. In those cases, growing tips produce abnormal lateral shooting and the development of witch's brooms. On heavily diseased trees, the surface of fruits shows a dramatic change in appearance.
Recommendations
Organic Control
Fungicidal sprays containing organic copper compounds like the Bordeaux mixture can be used to effectively combat this fungus. The first treatment should be done after the fall in the autumn season and again in spring before the buds start to swell. Note that repeated use of copper products can result in a buildup of copper in the soil, which eventually can become toxic to soil organisms.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatments, if available. Fungicides containing copper oxychloride, cupric hydroxide, thiram, ziram, chlorothalonil or difenoconazole can be used. The first treatment should be done after the fall in the autumn season and again in spring before the buds start to swell.
What caused it?
The symptoms are caused by the colonization of the plant tissues by the fungus Taphrina deformans. Spores produced on the leaf surface are washed by rain splashes or blown by the wind onto peach twigs and buds, initiating new infections. The spores germinate during frequent rains as the buds open in the spring and infect the still unfolded leaves. From the moment the spore enters the leaf bud, there is no effective countermeasure to stop the infectious process. If rain does not occur at this time, the spores remain inactive and little or no infection occurs. Lodged in bud scales or crevices in the bark throughout the summer and following winter, they eventually germinate during the next season. The fungus is only active at temperatures up to 16°C and can only reproduce at these low temperatures. Taphrina deformans infects peaches and nectarines, also almonds and occasionally apricots and ornamental Prunus.
Preventive Measures
- Protect the plants from rain or overhead irrigation during the bud swelling phase.
- Prune the tree crown every year to allow for proper ventilation of the foliage.
- Use moderate amounts of fertilizer.
- Use plant fortifiers before bud swelling.
- Plant resilient varieties, for example, white flesh varieties.
- Remove and destroy all obviously infected leaves, mummified fruits and shoots.
- Whenever possible, use a rain shelter of plastic to prevent infection.
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