See:
Peach (Prunus persica) - Leaf Curl
Cause The fungus Taphrina caerulescens is a common disease affecting many species of oaks. Members of the red oak group are particularly susceptible to infection. Disease development is favored by cool, wet springs. White oaks are rarely infected, even in years with cool, wet springs. Heavy infections of red oaks impair their appearance but do not endanger the tree's health.
Spores produced on the surface of the leaf spots in mid-summer are carried by wind and rain to the buds and become lodged under the bud scales. Here they overwinter. The following spring, they germinate and cause new infections. Infection occurs in the spring when tender, young leaves are exposed. Cool, wet weather is required for spore germination on young leaves, and if these conditions prevail, severe infection can occur. If weather conditions are not favorable for spore germination shortly after bud break, only minor infection will occur. As the leaves mature, they become more resistant to infection.
Symptoms Symptoms appear in early summer as yellow, circular, raised areas, 0.06 to 0.5 inch in diameter. The blisters are scattered over the upper leaf surface with corresponding gray depressions on the lower surface. They turn from yellow to reddish brown with pale yellow margins, and then become dull brown with age. Several blisters may merge and cause the leaves to curl. By midsummer, microscopic spores are produced by the fungus on the surface of the leaf spots, sometimes giving a white or light tan, powdery appearance to the lesions.
Cultural control
- Grow resistant species or cultivars.
- Increase spacing in nursery production.
Chemical control If needed, use once in the spring just before buds begin to swell.
- Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. H
- Daconil Weather Stik at 1.38 pints/100 gal water for red oaks only. Group M5 fungicide. 12-hr reentry.
- Mancozeb-based products. Group M3 fungicides. 24-hr reentry.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
- Ortho MAX Garden Disease Control at 2 teaspoons/gal water. H
- Rex Lime Sulfur Solution (28%) at 6 to 12 gal/100 gal water. 48-hr reentry. O
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
Reference Sinclair, W.A. and Lyon, H.H. 2005. Diseases of trees and shrubs, 2nd ed. Cornell University Press.