Fungal diseases occur in peach trees when an organism invades the tree. The fungus can kill the peach tree or infect the fruit with blemishes or rotting. Leaf curl, brown rot, blossom blight and peach scab are among the most common fungal diseases that affect the peach tree. Proper pruning and treating the tree with a fungicide may prevent the development of fungal diseases in peach trees.
Taphrina deformans, or leaf curl, is a common fungal disease in peach trees. Leaf curl on peach trees will make the leaves turn red or yellow, curl and drop from the tree. The tree is first affected in the early spring, when the spores of the fungus infect the leaf buds, and later, the fungus attacks the leaves themselves. A fungicide may help, if applied to the buds before they open.
Treatment for Leaf Curl
Additional nitrogen and heavy watering should be the first steps you take if you suspect leaf curl. Once you have made these stress-reducing steps, use a copper-based fungicide on the trees. Rake up the fallen leaves and burn them. Repeating the fungicide in the fall and spring will increase the chances of destroying the leaf curl spores.
Peach scab is caused by the fungus Cladosporium carpophilum. Peach scab is characterized by dark spots or cracks on the fruit, but they can be peeled off without affecting the fruit. Peach scab usually doesn't affect the peach tree leaves.
Treatment for Peach Scab
Prune carefully to prevent peach scab, trimming to allow for a good flow of air that will prevent moisture from building up on the branches and leaves. Follow up by treating the trees with fungicide for their first two years. The chemicals help control the spread of the disease include captan, azoxystrobin or a wettable sulfur. Read the label instructions carefully.
Brown rot, or Monilinia fructicola, is a serious peach tree fungal disease that can infect flower blossoms and shoots. It can be recognized by wilted blooms, and a brown spot on the fruit that starts out small and round, but quickly envelops the whole fruit. If infected pieces of fruit are left on the tree, they become what is known as a "mummy," and these mummies can house the fungus over the winter, enabling it to survive the cold weather and resurface the next spring.
Treatment for Brown Rot
Remove all infected peaches, both from the tree and on the ground. Do not put infected fruit or tree limbs in compost---this will only serve to spread the fungal disease. Apply fungicides, such as captan or azoxystrobin according to label instructions---complete and thorough coverage is a necessary.