Grow for it! Peach Leaf Curl
By Kit Smith
UCCE El Dorado County Master Gardener
Peach Leaf Curl is a fungus called Taphrina deformans. It infects both peach and nectarine trees. Overhead irrigation and rain wash the fungi onto buds and new leaves and from leaf to leaf. The Peach Leaf Curl fungus spores infect the trees through bud scales as the scales swell, and through shoots and leaves. In spring when peach and nectarine buds open, the fungus spores produce germ tubes that penetrate the young leaves. The fungus develops thick walls as they grow in leaf cells and ultimately break through leaf tissue.
Peach Leaf Curl prefers cool and wet weather to grow. Peach Leaf Curl thrives between November and March when temperatures are between a low of 48 degrees and highs of 79 and 87 degrees Fahrenheit. Optimum relative humidity for the fungus is 95 percent, very damp. It flourishes when the temperature is below 61 degrees Fahrenheit for 12.5 hours for two days duration. Infection stops when young growth on the tree stops and the temperature heats to between 79 and 87 degrees.
Peach Leaf Curl appears two weeks after leaves emerge from their buds. Leaves become yellow, warty and curled. They swell and pucker, and the twigs become distorted. Fruit production is reduced. When the fungus is apparent on peach or nectarine tree in the spring, it is already too late to treat the tree for the current growing season. You can take steps to help prevent Peach Leaf Curl from infecting the tree again for next year’s spring.
First, rake up and dispose of all old and dropped leaves. Peach Leaf Curl can overwinter in infected old leaves, bark and twigs. Plan to spray Liquid Copper or Liquid Lime Sulfur all over the tree and the ground. Spray three times: after there is at least 80 percent leaf drop, when the tree is dormant, and last to kill the spores before the tree buds open. An easy rule of thumb to help you remember when to spray is around Thanksgiving, Christmas (or New Year’s), and Valentine’s Day. Be sure there is no rain is in the forecast for at least 24 hours, and always carefully follow all label instructions.
If the winter is particularly wet, spray a second time late in tree dormancy when the buds begin to swell.
Spray annually. Repeated infections of Peach Leaf Curl will cause defoliation or loss of leaves, and could cause the death of your tree. Leaves are very valuable to the life of your tree for photosynthesis; the process that turns sunlight, water and carbon dioxide into food energy for your tree. Take positive steps to keep your peach and nectarine trees healthy.
Master Gardeners are available to answer home gardening questions Tuesday through Friday, 9 a.m. to noon, by calling (530) 621-5512. Walk-ins are welcome at our office, located at 311 Fair Lane in Placerville. For more information about our free public education classes and activities, go to our Master Gardener website at ucanr.edu/sites/EDC_Master_Gardeners/. Sign up to receive our online notices and e-newsletter at ucanr.edu/mgenews/. You can also find us on Facebook.