Dorothy is a Master Gardener, former newspaper reporter, and the author of several books. Michael is a landscape/nature photographer in NM.
Recognizing Peach Leaf Curl
- You are not going to have to be a rocket scientist for this one. Peach leaf curl targets only peach and nectarine trees, and it is pretty easy to spot. It is, by far, one of the worst diseases your peach tree could have, and it usually occurs in the springtime when the weather is cool and wet.
- New peach leaves will be very thick (abnormally so) and, as they grow, they begin to curl and have a "puckered" look to them. On the leaves, you will find blisters that will later turn white. The blisters will usually start out as yellow or reddish. Later, the whole leaf can turn different colors while at the same time developing a whitish covering.
- In early summertime, those already-ugly leaves will get even uglier as they turn black, shrivel up completely, and fall. Sometimes, after the infected leaves fall, another crop of leaves can form on the tree, but trees that are infected are weak and produce fruit (if you get any) that will be misshapen and covered with lesions in varying shapes.
- This fruit will drop before it ripens and several years of the disease will make your peach tree severely weak with a reduction in the amount of fruit you are able to find usable. Usually, the tree won't die, but you may wish it would.
Named the May 2018 "Disease of the Month"
In order for a plant disease to be named "Disease of the Month," it must be of great concern to a lot of people. Peach leaf curl has/had the distinction in May 2018 of having that title, bestowed by the Pennsylvania State University's College of Agricultural Sciences. Reporting on their website state that this disease was the one that was frustrating people the most.
Spores that are produced on the surface of the leaf as the leaf matures will give the leaf a dusty appearance. The fruit can be infected and will either drop prematurely or be distorted on the surface.
The spores are able to overwinter in bark crevices and around the peach buds and the primary infection occurs from the time the buds swell until the first leaves completely emerge. Any occurrence of rain will wash the spores into the buds. The primary infection can occur during long periods of cool weather (50-70 degrees Fahrenheit) or wet weather (greater than 95% humidity), both creating conditions that are ideal for the infection. Chances of infection are minimal, however, when the temperature is below 45 degrees Fahrenheit. Luckily, infections are rarely established if warm temperatures follow bud swell and rapid leaf development, even in the case of rain.
This is a disease that says "Hello, I'm here!" and can be spotted easily from 20 yards while in a moving vehicle.
— Kari A. Peter, Ph.D. Assistant Professor, Tree Fruit Pathology, Pennsylvania State University
Peach Leaf Curl at Its Worst
Why Treatment Is Ineffective
If you have peach leaf curl on your trees, treatment will be ineffective because the leaves protect the spores around the buds. You will need to wait until the end of the season to manage this aggravating disease. If you have a severe case of the disease, it is very important that you maintain tree vigor by thinning more fruit than normal. Be sure to irrigate to reduce any stress caused by drought and apply extra nitrogen fertilizer to the soil.
Preventing Peach Leaf Curl in the Future
There are certain varieties of peach and nectarine trees that are resistant to peach leaf curl, and I suggest you seek those out in whatever zone you are in, as I expect different varieties will be more or less resistant depending on your zone.
If you've had infected trees before, you should always use a dormant-season fungicide, one that contains lime sulfur spray (or a Bordeaux mixture), but you will need to wait until the last leaf falls. Then, in the spring, spray them again before any new leaves appear. If you wait until buds are open on the tree before using a fungicide, you have waited too long and there is no need to spray again.
For severe infestation, a fungicide spray in the late fall and late winter or early spring might effectively manage peach leaf curl.
If you have peach orchards, you will need to wait until almost all of the leaves have fallen or before bud swell in the spring to attempt to control the disease. During those times, applying a fungicide (chlorothalonil) or copper spray would be appropriate.
Growers in future seasons will have to monitor the upcoming February temperatures closely because if temperatures are forecast to be above average, the dormant fungicide spray will need to be applied prior to those warmer days in order to effectively control the fungus around the buds.
The most effective prevention will usually consist of planting only stock that has been acquired from reliable nurseries and pruning any twigs/leaves that have signs of infection.
- https://extension.psu.edu/disease-of-the-month-peach-leaf-curl (retrieved from website 05/07/2018)
- Rutter, John The Culture and Diseases of the Peach: A Complete Treatise for the Use of Peach Growers
- http://homeguides.sfgate.com/identify-peach-tree-disease-50796.html (retrieved from website 3/27/2018)
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
Questions & Answers
Question: I have curl on my peach trees. How should I treat them?
Answer: Leaf curl can be controlled by applying sulfur or copper-based fungicides that are labeled for use on peaches and nectarines. Spray the entire tree after 90% of the leaves have dropped in the fall and again in the early spring, just before the buds open. I have a peach tree and keep holding my breath every time I look at it, but so far, so good.
© 2012 Mike and Dorothy McKenney