| Peach -- Leaf Curl | ||||
| Cause:
Taphrina deformans, a fungus. Spores overwinter on bark, twigs, and old infected leaves. Infection occurs through bud scales in mid- to late winter just as buds begin to swell or on slow growing shoots and leaves during a cool and wet growing season. Maximum susceptibility is between bud break and petal fall. In wet seasons, the organism continues to cause slight summer infection, particularly west of the Cascades. East of the Cascades, after the initial spring infection and the shedding of diseased leaves, no further evidence of the disease is visible.
Defoliation from severe infections weakens trees to the point that, if not controlled, they may die in 2 to 3 years.
Wetness from rain (or other factors) for over 12.5 hours is needed for leaf infection but only when the temperature is below 61°F during the wet period. Maximum infection occurs when trees are wet for 2 days or more, a frequent occurrence west of the Cascades. Although infected, symptoms may not appear if temperatures remain above 69°F. Fruit are susceptible after petal fall until air temperature remains above 61°F. Rainfall of 0.5 inch and wetness of 24 hours is needed for fruit infection. |
||||
| Symptoms:
The first visibly infected leaves are yellow to reddish and somewhat thickened and crisp in texture. As they develop, they produce a dusty white coating of spores. Infected twigs occasionally are distorted, and a few fruit may show a reddish growth on the surface. Some infected leaves drop; others remain throughout the growing season, gradually becoming dark brown and heavily coated with spores. In wet seasons, the organism continues to cause slight summer infection, particularly west of the Cascades. Ultimately, many infected leaves are shed. East of the Cascades, after the initial spring infection and the shedding of diseased leaves, no further evidence of the disease is visible. Defoliation from severe infections weakens trees to the point that, if not controlled, they may die in 2 to 3 years. Ultimately, many infected leaves are shed. Trees die in 2 to 3 years from repeated defoliation. |
||||
|
||||
| Cultural control: ‘Frost’ is reportedly resistant but must receive fungicide applications the first 2 to 3 years. The late-ripening cultivars ‘Muir’ and ‘Krummel’ are tolerant but as of 2003, Krummel was not easily available from nurseries. | ||||
Chemical
control: Two fungicide applications are recommended for western Oregon: at 50% leaf fall (late October), and again at delayed dormant (usually in late February, before floral buds open). A third application may be needed during the dormant season for shothole control depending on materials selected. In Washington, apply three times 3 weeks apart starting in early January. East of the Cascades and in low rainfall areas, a delayed dormant application alone should be effective.
|
||||
|
References: Rossi, V., Bolognesi, M., Languasco, L. and Giosue, S. 2006. Influence of environmental conditions on infection of peach shoots by Taphrina deformans. Phytopathology 96:155-163. Rossi, V., Bolognesi, M., and Giosuè, S. 2007. Influence of weather conditions on infection of peach fruit by Taphrina deformans. Phytopathology 97:1625-1633. |
||||
| Content edited by: Jay W. Pscheidt on January 1, 2009 | ||||
In print since 1954 and on the web since 1996. Questions or comments, please contact us.