What Is Peach Leaf Curl?
Peach leaf curl, also known as curly leaf, curly blight or leaf blister, has been recognized as a common disease since the early 1800s. It is caused by the fungus Taphrina deformans and can affect the blossoms, fruit, leaves and shoots of peaches and nectarines. Peach leaf curl is the most common disease found in backyard orchards. Cool (48-68°F) wet weather when leaves are first opening favors the disease. Watch our video on Peach Leaf Curl where Tricia shows how to care for your trees. 
Life Cycle of the Fungus
Symptoms appear after leaves emerge and begin to grow. The fungus causes cells in the infected portions of the leaves to grow abnormally large, causing the distorted look to the leaves. The fungus eventually produces reproductive bodies called asci that contain the spores. You will see a velvety-like appearance to the leaves, this is caused from the spores or ascospores. They are released into the air and infect other parts of the tree or other trees. In the newly infected areas the fungus continues to multiply and "cover" the tree and remain dormant in the bark and around the buds. The following spring the fungus is moved by rain or irrigation and infects new leaves. And the cycle continues. If not treated, the infection can weaken the tree and cause a decline in fruit production. 
Treatment for Peach Leaf Curl
Chemical controls
Copper
Products available to the home orchardist are those with lower Metallic Copper Equivalent (MCE) of about 8%, such as Liqui-Cop. Effectiveness can be improved with a sticker such as Horticultural Oils. Follow the instructions for all products and make sure you use appropriate safety equipment during application. Apply fungicide to point of runoff and a good rule of thumb is to apply three times during the dormant season: after leaf drop (around Thanksgiving), winter (around Jan.1) and before bud swell (around Feb, depending on where you live). You can apply less often if the infection the previous year was light.
Lime Sulfur
Effective for controlling peach leaf curl but not registered for sale for the backyard orchard and not available for sale in many states.
Cultural Controls
Once the tree is infected there is not much to be done to get rid of the disease that season. But it is very important to maintain the vigor of the tree throughout the active growing season.
- Thin the fruit to reduce the demand on the trees' resources. For peaches and nectarine, thin fruit to at least 3 inches apart. Remove diseased or cracked fruit and place in the trash, not your compost pile.
- Fertilize with nitrogen by mid-June, a good balanced fruit tree fertilizer is a good choice.
- Keep watered to reduce water stress.
- Clean up dropped leaves or fruit around the base of the tree to reduce spreading to other trees. Don't put these in the compost pile, the spores can remain dormant for some time.
Another option, especially if you have to remove a weakened tree, is to consider putting in resistant or partially resistant varieties such as Frost, Indian Free, Muir, or a multigraft peach tree that contains all those varieties. If you don't care for these varieties, choose a tree that blooms later in the season. You may see less disease developing in these due to the later bloom time.
Don't let peach leaf curl ruin your favorite peach or nectarine. Yearly spraying with a fungicide listed for peach leaf curl will keep the disease in check and allow for a healthy tree and a bountiful harvest.
14 comments
Dan, you can remove the leaves that are affected by the curl and put them in the trash (not your compost pile). If you use pruners to remove the leaves, make sure that you disinfect the pruners. You don’t want to transfer anything to the healthy tree. I would not destroy the tree, just treat them next winter, clean up any leaves around the trees, don’t handle the diseased tree, then handle the healthy tree.
Thanks for your suggestions about peach leaf curl. One you didn’t mention for the backyard gardener, which has worked well for me, is to simply pinch off any sign of curl on the leaves as it first appears. I sometimes pinch off the affected parts only, leaving the remainder of the leaves, and sometimes pinch or cut off whole leaves and new shoots obviously stricken. As I work my way around the tree, I put the infected growth in a paper sack, which then goes into my woodstove to prevent further contamination.
This pruning lets the tree continue to grow normally and eventually overwhelm the fungus for the season, as conditions dry. I have had great crops of peaches using this method for more than ten years. The fungus generally has returned the following years, since I live near the coast along a wetlands in central California (ideal fungal conditions, I would say), but does seem to be diminishing.
I have a young peach tree seedling, about 2-3’ tall that I grew from a pit/seed and does not yet bear fruit. It has this leaf curl problem. Is there someway to treat the leaves and tree now instead of waiting until fall/winter or next spring?. It pains me to see it struggling and not being able to do something!
M, well the infected leave will eventually fall off and you should clean up all of the dead leaves. Put it in your trash and not your compost pile. You can make sure that your tree has sufficient nutrients to recover from losing the leaves. So add some fruit tree fertilizer. Some people like to spray their trees with compost tea as well as fertilizing. All will help the tree be as strong as it can be to recover from the disease.