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Why does peach leaf curl keep growing back on my tree?

Leimone Waite
Master gardeners
A healthy peach tree bears healthy fruit.

Q:  I have a peach tree that keeps getting peach leaf curl every spring. I have sprayed the tree in past winters but my tree still gets badly infested. What am I doing wrong?

A:  Severely affected shoots will die. Your treatments may not be effective due to the timing of the treatments or the type of material you are using for a dormant spray. Peach leaf curl is a fungal disease that causes leaves to become thickened, curled, and colored red or yellow instead of normal green. There is no direct treatment just prevention with a dormant spray that will kill fungal spores overwintering on the tree branches.

The University of California Home Orchard site recommends spraying at least twice during the dormant season, the first of December and again the first of February just before the buds begin to open. One way to remember when to consider dormant spraying is to do so around Thanksgiving day and Valentine’s Day and if you have a considerable disease problem the previous year, you might add another spray around New Year ’s Day.

Peach leaf curl

There are two types of dormant sprays one is a fixed copper spray such as, Kop R Spray Concentrate and Liqui-Cop, and the other type is a dormant oil spry. Dormant oil sprays have a variety of names depending upon the manufacturer and/or desired pest or disease control. Dormant spray oils are also known as horticultural oil, insecticidal oil, narrow range oil, supreme oil, superior oil, dormant oil or ultrafine oil and can be used in ornamentals, fruit and nut trees.

Most oils are used to control soft bodied insects such as aphids, immature white flies, immature scales, psyllids, thrips and some insect eggs as well as mites but certain horticultural oils can help control leaf curl, shot hole fungus, powdery mildew and other fungi. Fixed copper sprays are used to control fungal diseases like peach leaf curl or shot hole.  

Regardless of the type of dormant spray, thorough application and coverage is essential for successful treatment of both disease and insect problems. Trees should be sprayed until all branches are thoroughly wet and dripping. 

When applying dormant sprays it is important to wear personal protective gear and long sleeves and long pants as you want prevent skin exposure and avoid inhaling or getting spry in your eyes. Time spaying the tree so that you will have several dry days following the application as sprays are less effective if immediately washed off by rain.

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Additionally, dormant sprays may not be needed every year in a backyard orchard. The previous season will help you decide if the amount of disease and insect damage warrants spraying.

The University of California Home Orchard site has a detail list of pests by tree species and what type of dormant spray will best control each one. It can be found here: https://bit.ly/36feNzS.

The Shasta Master Gardeners Program can be reached by phone at 242-2219 or email mastergardener@shastacollege.edu. The gardener office is staffed by volunteers trained by the University of California to answer gardeners' questions using information based on scientific research.