When to spray dormant peach trees


Question: When do I have to be dormant to spray my fruit trees? Earlier this year I asked about peach leaf curl on my peach tree and was told that prevention in the form of at least two dormant sprays was the best treatment, but I can’t remember when I had to spray. Is it too early to start?

A: Peach leaf curl is a disease of peaches and nectarines that causes their leaves to curl and deform. In poor infestations, it can cause defoliation, crop loss, fruit damage or loss of tree branches.

Peach leaf curvature affects the flowers, fruits, leaves, and shoots of peaches, ornamental flowering peaches, and nectarines, and is one of the most common disease problems for gardeners who grow these trees.

The curvature of peach leaves is caused by a fungus called Taphrina deformans. This fungus thrives between November and May, when daytime temperatures range from 48 to 87 degrees Fahrenheit and we have cool, humid weather. Once temperatures warm beyond 87 degrees Fahrenheit, or relative humidity drops and things dry out, the new leaf infection stops. Leaf buds and young leaf tissue, the most susceptible to symptoms, will also stop when the leaves stop developing. Once you start to see the yellow, warty, and curly leaves, it is too late to treat the disease that year. As the disease progresses, the cells in the leaf swell and wrinkle, and the twigs become deformed. With severe infections, fruit production is drastically reduced, and the skin surface of the fruit may develop cork-like cracks and bumps.

Prevention is the best treatment. The spores of the fungus infect trees through the scales of the buds. These are the protective sheath around each leaf bud. In cool, humid weather, the spores multiply on the scales and bark of buds, then infect shoots and leaves as they emerge in the spring. Once the peach leaf curl fungus is on the peach leaf, it produces germ tubes that penetrate the young leaves, causing the leaves to deform.

Peach leaf curvature affects the flowers, fruits, leaves, and shoots of peaches, ornamental flowering peaches, and nectarines, and is one of the most common disease problems for gardeners who grow these trees.

By treating the trees with a good dormant spray during the winter and early spring, the fungus is killed, preventing it from overwintering and infecting new growth in the spring.

To treat your trees, spray until they drip with a copper-based dormant spray three times during the winter months. These treatments should be staggered during the dormant season.

  • Plan to make the first spray now, around Thanksgiving, after the tree has dropped its leaves for the winter.
  • Spray again about a month later around New Year’s Day.
  • Spray one last time just before Valentine’s Day.

Before the first spray, collect and dispose of all old and newly fallen leaves. If the tree was severely infected this summer, prune it now to reduce the number of spores that will overwinter. When spraying the tree, also spray the trunk and the area under the tree. After cleaning around the tree, place a new layer of mulch under and around it to prevent fungal spores from spilling out onto the tree.

Avoid spraying if rain is forecast. The rain washes the dormant spray from the tree. Dormant sprays work best if they can sit on the tree for several days before the rain washes them away.

As always, please follow all label directions when using any type of fungicide or pesticide.

Following:Weed Control: How To Protect Your Lawn From Invasive Plants

For a more in-depth discussion of peach leaf curl, please see the University of California Pest Notes for Home and Landscape at https://bit.ly/30NdFDQ.

These healthy peaches are ready to be picked.

The Shasta Master Gardeners program can be contacted by phone at 530-242-2219 or by email at [email protected] The Gardener’s Office is made up of volunteers trained by the University of California to answer gardeners’ questions using information based on scientific research.


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