Now that the holidays are behind us, many gardeners are turning their attention to the New Year and their high hopes for a bountiful backyard harvest. Fresno's short winters mean now is the last chance for stone fruit-growing gardeners to prevent peach leaf curl disease, which causes leaves to drop and fruit production to wane. 

Once new buds begin to open and tiny deformed leaves unfurl in the spring, it's too late to manage the disease. Fortunately, peach leaf curl can be easily treated with a fungicide during the dormant season and, in any event, rarely kills trees. 

The disease impacts peach and nectarine trees. A severe outbreak of peach leaf curl won't happen every year. But it's not uncommon to have wet weather when buds and leaves begin to grow, providing the best environment for the fungus to germinate and spread. 

The fungus that causes peach leaf curl, Taphrina deformans, is widespread in the valley. The fungus survives the summer as spores on twig and branch surfaces. During cool, wet winter weather the spores increase in number and form a film on the tree surface. Rains carry some spores into unopened buds where they infect the tiny leaves.?Leaf and fruit removal do not contribute to peach leaf curl control. 

The UC Integrated Pest Management Program recommends gardeners spray trees with a fungicide containing copper or chlorothalonil, which are readily available in many nurseries and home improvement stores. One annual application in late winter before budbreak will control the disease in most cases. Alternating the two fungicides each year can help to limit copper buildup in the soil. Horticultural oils and other fungicides are not effective against peach leaf curl. Copper, but not chlorothalonil, is approved for organic gardening. 

Carefully read the label on the product you purchase and follow instructions for mixing and using the product. A hand-held pump sprayer will work fine for smaller trees. For larger trees, consider a hose-end sprayer. Dress in protective clothing, including long pants, a long-sleeved shirt, gloves and safety goggles. Spray the trees when the weather is dry and mostly windless, making sure to wet the branches and the trunk thoroughly. 

For more information about growing fruit trees at home visit the UC Backyard Orchard website at https://homeorchard.ucanr.edu/