Did your peach tree have distorted, reddened leaves this spring that maybe fell off and grew back this summer? If so, your tree may suffer from a fungal disease called Peach Leaf Curl. You can get more information about the disease symptoms and management from the UC Pest Note If your tree does have peach leaf curl, the best time to apply a preventative fungicide is in November after the leaves have fallen. You can apply a copper ammonium spray such as Liqui-Cop or Kop R Spray. Make sure you follow the label and wear appropriate personal protection. If you wait til the symptoms appear again next spring, it's too late to control the disease.