Problem: Fire Blight (Apple)
This disease is caused by a bacterium (Erwinia amylovora) that commonly affects apples, pears, and several ornamental plants. The bacteria overwinter in cankers on branches and twigs. Just before the tree blooms, bacteria ooze out of the cankers and are carried to the blossoms by splashing rain and insects. Honeybees continue spreading the bacteria to healthy blossoms. Summer storms can also spread bacteria, leading to sudden and severe fire blight outbreaks. Bacterial decay causes cankers to develop on twigs and branches, often resulting in conspicuous dieback.
Prune infected twigs and branches at least 12 inches beyond visible decay, and destroy the debris. During the growing season, disinfect pruning shears after each cut.