Peach Leaf Curl

• Peach leaf curl, sometimes called leaf curl, also infects nectarine trees. It is a disease caused by a fungus that requires lots of moisture and mild temperatures -- between 50 and 70 degrees Fahrenheit -- to germinate. The name of the disease describes its earliest and most apparent symptom: curled, distorted foliage. A tricky pathogen, symptoms disappear when the air dries and temperatures rise, only to return again when conditions suit it. Once the fungus -- Taphrina deformans -- gets into the foliage, it can't be killed, so preventive fungicide spray programs are recommended.
  
  

Frequency

• Peach and nectarine trees generally only require one fungicide application, if timed correctly. Since the initial infection is the most severe, and occurs in early spring when the buds swell, timing the fungicide application is of the utmost importance. Spray the tree in the fall after almost all of the leaves fall. The second best time to treat the tree is in spring just before the buds swell. It is perfectly acceptable to treat the tree in both fall and spring, especially if you live in an area that receives a lot of spring rain. Spraying fungicide at other times during the season is ineffective and typically a waste of money.
  
  

Fungicides

• The ideal fungicide for the treatment of peach leaf curl is one that contains chlorothalonil or fixed copper, such as copper ammonium, as the active ingredient. Organic farmers can use Bordeaux, but it isn't as effective as chemical-based fungicides and requires repeated applications. The University of California has a Bordeaux formula on its website. If you purchase a commercial formula, read the label and apply according to the schedule listed. The cooperative extension service in your county offers excellent information on fungicides to use in your region and in your particular situation.
  
  

Application

• Use a tank sprayer to apply the fungicide. Calibrate the pressure before adding the ingredients to the tank. The instructions that came with the sprayer will assist you in this task and the fungicide label should list the ideal pressure. If the fungicide is to be mixed with water, add the water to the tank first and then add the fungicide, swirling the tank as you pour it in. As you spray the tree, pay close attention to the crevices in branches and twigs as this is where the spores overwinter. Spray the entire tree until it is drenched, unless the fungicide label says otherwise.