In the Garden:
Southern California Coastal & Inland Valleys
Peach leaf curl is a fungal problem easily prevented by dormant spray.
Dormant Spray for Tree Pests
Plan your dormant fruit tree spraying schedule to coincide approximately with cool-weather holidays -- Thanksgiving, New Year's Day, and Valentine's Day. Specific cues are the fall of the last leaf (Thanksgiving), the height and depth of dormancy (New Year's Day), and bud swell (Valentine's Day). The point is to have the sprayed material on the tree throughout the dormant season.
Spraying the last application at the precise period of bud swell is especially important. This is usually during early to mid-February for us. Before the buds swell is too early, and after the blossoms open is too late. The perfect moment is when the buds are swollen but don't yet show color. Once the buds open, the damage has already been done.
The Right Spray for the Job
Oil sprays smother the eggs of scale insects, aphids, and mites. Lime sulfur and powdered or liquid copper sprays discourage the growth of fungus (including peach leaf curl) and virus. Choose a copper spray that contains at least 50 percent copper.
For peach leaf curl, choose a fungicide such as Bordeaux, a mixture of copper sulfate and lime. For apricot trees, use only copper sprays, since sulfur will damage them.
If the rains haven't thoroughly moistened the soil of trees to be sprayed, water them deeply few days before spraying. The oil spray may damage the trees if their roots are too dry because moisture is needed to help the roots absorb the nutrients.
Spray on a cool, dry, sunny day when the temperature stays above 40 degrees and there's no wind (which minimizes evaporation and drift). Make sure that all leaf, branch, and trunk surfaces are thoroughly covered with the spray solution. Drenching the soil from the trunk to just beyond the drip line is also helpful. Reapply if rain falls within 48 hours of the application.
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