Advice for Home Gardeners from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Help Desk Response: Thanks for contacting the UC Master Gardener Help Desk about the problem you are observing on your nectarine tree.
Your nectarine tree is showing the classic symptoms of a fungal disease commonly called "peach leaf curl". It is a common problem for both peaches and nectarines, particularly in years when we have abundant rains as has now occurred this year. The fungal spores that spread the disease can be spread through splashing water and rain.
As you may already have noticed, typically the affected leaves turn yellow or brown and can remain on the tree or may fall off; they are replaced by a second set of leaves that develop more normally unless wet weather continues. Most often the disease will not show up on the developing fruit, but occasionally it does affect fruit, causing corky areas to develop on the fruit surface. Those fruits are still okay to eat—just cut away the affected area.
Unfortunately, there is nothing you can do now to stop the disease on your tree. The typical management approach for controlling peach leaf curl is to use a fungicide in the late fall or early winter months when the tree is dormant. The use of fungicides when the tree is dormant can control the development of the spores that usually survive the hot summer months on the surface of the tree bark. Those spores are reactivated by winter rains and attack the leaves when they emerge in the spring. You should plan now to consider applying such a fungicide in early December, particularly if we are having frequent rains. Just try to schedule the fungicide spraying for a time when you expect to have several successive days of dry weather so that the fungicide can work and not be washed off the tree. You can learn more about peach leaf curl and the use of fungicides to control it at this University of California website: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7426.html
Since fungal spores may also be present on the fallen leaves, it is a good idea to pick up all fallen leaves. Don't put them in your compost pile unless you have a pile that regularly achieves and maintains high temperatures. If your compost piles doesn't have those high temperatures on a regular basis, you can dispose of the leaves in a green bin that goes to a waste company's compost area. Fortunately, those sites typically have compost piles that achieve the high temperatures needed to kill fungal spores.
If you have not yet fertilized your tree, this would be a good time to feed. Just be careful not to use too much fertilizer. It would be better to use less now and re-apply some additional fertilizer is about a month or six weeks. Here's a link to more information on peach tree care: http://homeorchard.ucanr.edu/Fruits_&_Nuts/Peach/ which also applies to nectarine trees.
We hope that this information is helpful. You're welcome to contact us again if you have other questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (TKL)
Note: UC Master Gardeners Program of Contra Costa's Help Desk is available almost year-round to answer your gardening questions. Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone: (925) 608-6683, email: email@example.com, or on the web at http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog.
Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa
Client: I have 5 different varieties of nectarine and peach trees in my Central CCC backyard. I treat the trees in late winter for peach leaf curl using an organic - approved spray. That works great.
What do you think the problem is? What is the cure? I prefer to use organic methods.
Advice from the MGCC's Help Desk: Thanks for contacting the MGCC Program's Help Desk. From your description, the problem with your nectarine fruit appears to be caused by the “brown rot fungus”, monilinia fruiticola. Peaches can be attacked by Brown Rot as well.
Brown rot fungus is tough and can survive over the winter:
- in infected twigs
- inside dead blighted blossoms that remain on the tree
- dry mummified fruit that has been left on the tree from the previous year
- dry mummified fruit left on the ground from the previous year
Brown rot infection and disease development can take place over a wide temperature range and flowers can be infected from the time buds open until petals fall. Water must be present on the flower surface for infection to occur. Spores produced on the tree parts described above in spring are carried through the air by wind and splashing water to infect flowers of the new year's crop.
Appropriate applications of fungicide is the usual preventive measure to prevent brown rot, especially if you've had it occur before. However, fungicides can only prevent brown rot; they will not cure brown rot so timely application is important. Organic fungicides do not appear to be readily available for home gardeners. Recommended applications of copper-containing fungicides or synthetic fungicides such as myclobutanil at pink bud stage - just before the buds open can help avoid serious fruit losses. Rainy periods will require more spray. Additional applications when fruit starts to color may be needed if rainy weather persists. Do not apply copper compounds after bloom.
More specific information can be found by following the links below:
Good luck this year with your nectarines. Hopefully, pruning, sanitation, cultural care, and a timely application of a fungicide will minimize brown rot.
Please let us know if you have any further questions we can help you with, and thank you for contacting our program!
Help Desk of the UC Master Gardener Program of Contra Costa (JMA)
Note: The UC Master Gardeners of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).