"Blight" is the word used to describe any plant disease where rotting does not take place. Therefore, blight in peach trees can refer to any number of diseases that affect the health of the tree without causing the flowers or fruit to rot. Such diseases may affect the tree in a minor aesthetic way or they may be much more serious, causing a loss of crops.
Blight diseases can be fungal, viral or bacterial in nature. Fungi that infect peach trees can live in the soil and attack the roots, or they can spread through the air on water. Sometimes fungal spores overwinter on the tree, hiding in tiny cracks in the bark. Bacterial and viral diseases often enter a tree on the bodies of insects or from tainted pruning or gardening tools.
Peach leaf curl is a fungal disease that commonly affects peach trees. This blight causes defoliation of the tree, severely hindering fruiting. Affected trees have leaves that develop lesions and curl inward. Infected peaches will drop before they can fully develop, according to West Virginia University. Plum pox virus affects peach trees, as well as other stone fruits, and lives in the mouths of aphids. Infected trees will show striations and discolorations in the leaves and fruit. Fusicoccum canker is a fungal disease that infects the wood, causing twigs and parts of branches to become sunken, blackened and cracked.
Prevention is the key to keeping your peach tree blight-free. Controlling insects is one way to ensure viruses aren't transmitted, according to Cornell University. Spray your tree with an insecticide approved for use on stone fruit at the first sign of insect activity. Sterilize pruning tools with bleach between each cut, and take care to avoid injuring the bark of the tree with lawn tools. Even a small nick might be large enough for fungal spores to enter the sapwood of the tree. Finally, water at the soil level and locate your peach tree where it will receive morning sunlight to quickly dry the dew off of the leaves. In addition, make sure there is plenty of room around your tree for air circulation. This will reduce the chances of a fungal disease developing.
Many blights can be treated before they infect the entire tree. Prune off obviously infected branches that contain withering or spotted leaves. Remove branches with cankers by cutting at least an inch below the canker. Soil drenches can kill fungi living or overwintering in the soil, and timely applications of fungicide can prevent fungi from gaining a foothold on your peach tree.
Some types of peach trees are more resistant to blight than others. These hardy trees are the best choice for climates that may be more prone to fungal diseases, such as those that have warm, wet spring weather. These cultivars are also the best choice for beginning home gardeners. Coronet, Sunhigh and Harken are all very hardy and blight-resistant peach tree cultivars, according to West Virginia University.