Leaf Curl of Peaches

By Bob Chapman

Peach leaf curl is found on both peaches and nectarines but there are many other plants and trees attacked by this disease. The list includes such popular plants, shrubs and trees like alder, apricot, azalea, birch, camellia, fruiting and flowering cherries, elm, ferns, maple, nectarine, oak, plum, poplar, rhododendron and willow. Here are some suggestions about ridding your peach tree of this sometimes-fatal disease and preventing it recurrence.

The disease in various stages of development

When infected with leaf curl the emerging shoots are swollen and stunted. Initially the infected foliage is red or orange, but later turns pale green to yellow. As the season progresses, a grayish white powdery material develops on the leaves.

The infestation can be severe enough to cause leaves to drop. Fruiting may be poor and those that develop may be covered with raised, irregular or wrinkled lesions. Infected trees are greatly weakened by the premature loss of leaves, the food-producing parts of the tree. The disease is worse when wet springs occur.

Life cycle of Taphrina deformans

To understand why there is no cure you have to understand how the disease organism infects the tree. The disease is caused by a fungus, Taphrina deformans, which attacks both peaches and nectarines. Infection of the tree occurs as soon as the buds begin to swell in the spring. Fungal spores are carried by wind or splashed from the bark to the buds by rains. Later, the infected leaves develop a grayish-white covering of spores that are then blown onto the bark and lie there waiting until next spring to invade the host plant, your peach tree. Once inside the infected leaf there is no way to kill the fungus.

Preventing leaf curl

Peach leaf curl can only be prevented by spraying the trees in the fall after the leaves have fallen and again in the spring before the buds begin to swell and before they open. There is no "cure" for peach leaf curl once the buds on the trees have opened.

The U.C. Cooperative Extension Service states that the only really effective spray is a copper-based fungicide. One successful combination is Kop-R-Spray and a sticker-spreader such as Natures Own Spray Helper. There are other sprays on the market, such as lime/sulfur or Bordeaux spray, a copper/lime formulation, and all have their devotees.

Hope for infected trees

Many trees over the years will overcome a severe infestation when a spraying program was initiated in the fall following an outbreak and then spraying before bud break in the spring. These trees rebound and produce fine crops of peaches in the summer.

Summary

-- There is no cure for peach leaf curl once the leaves are infected.
-- Prevent peach leaf curl by spraying in the fall and again just before bud break.
-- The suggested combination is Kop-R-Spray and Natures Own Spray Helper.
-- Even severely infected trees will survive, but do spray next season to prevent future         infection next year.  

Bob Chapman is a well-known professional gardener and landscape contractor. Currently retired, Bob now spends his time contributing many free-lance garden articles and columns, and is a much sought after lecturer and horticultural consultant.

Since 1987, Bob has appeared as a regular columnist for the San Jose Mercury News. Besides the Mercury, his writings have appeared in the San Diego Tribune, Sacramento Bee, Fresno Bee and the Times Newspaper Group. He is the 1991 winner of the Quill and Trowel Award of the Garden Writers Association of America for the best newspaper gardening article in North America.

Bob majored in Ornamental Horticulture at Cal-Poly, San Luis Obispo. He also served as a member of the Professional Gardeners Association.