Peach trees experience three major fungal diseases that can cripple the tree's production for the year and ruin your peach harvest if not caught and treated. Gardeners must learn to identify the symptoms of disease so they can act quickly if they think trees are infected. Fungal diseases can overwinter in the soil, so dispose of any fallen leaves or branches to improve your chances of tree health.
When peach trees get leaf curl, the leaves shrivel up and curl inward, taking on a crinkly appearance. Some leaves remain green while others turn tan or brown. Gardeners can control for peach leaf curl by spraying preventative fungicides containing copper or lime sulfur. However, they must apply copper-based spray before the buds and leaves open. Peach leaf foliage is sensitive and can be further damaged by a late application of copper fungicide.
Brown rot affects the peaches and can destroy a peach crop. This disease develops in the presence of wet weather. Affected fruit displays fuzzy brown splotches on the skin. North Carolina State University notes that brown rot can cause the most damage just before the peaches are ready to harvest. Brown rot can be controlled by applying a sulfur fungicide every five to seven days, or use two doses of a fungicide containing myclobutani (be sure it does not also have insecticide). Follow the dosage recommendations on the appropriate treatment package.
The same fungus that causes brown rot of peaches can cause blossom blight if it strikes earlier in the season. The treatment for blossom blight is the same as for brown rot. Affected blooms shrivel up and turn dark brown. They remain on the branch. Some leaves may wilt and develop a dried-out texture.
If your peaches look like they've been covered in small brown freckles or moles, they have peach scab. By the time these symptoms are noticeable, it's too late to do anything to save the peach crop. Earlier in the season, peach tree twigs will develop small cankers. This is the only other early symptom of peach scab that gardeners can find. If your peach tree has experienced peach scab in the past or if there is a problem in your area, the disease can be controlled by spraying preventative fungicides every 10 to 14 days using a sulfur or wettable powder fungicide.
Gardeners should keep their peach trees healthy to ward off disease naturally. Peach trees benefit from annual pruning to remove dead or unhealthy wood and open up the canopy to improve air circulation. This helps move fungus through the tree; trees that have been neglected are more apt to trap fungus in their branches. Fertilize peach trees annually and irrigate trees so they are healthy and not stressed. Use an appropriate fertilizer based on your soil's nutrient levels and the age of your peach tree. If you don't know what to use, contact your local county extension office for a soil test.