Late spring and early summer are the time fire blight shows itself. Fire blight is a bacterial disease that makes plants look as though they have been damaged by fire. It attacks apples, pear and quince, most often, but can also infect ornamentals, such as toyon and pyracantha. Very often, the growing tip folds over into a shepherd’s crook shape.
Fire blight spends the winter in cankers or wounds on the plant and resumes bacterial growth in the spring. There may be oozing from the canker. It is spread by insects, rain, or pruning. Infection can extend into limbs, trunks, or the root system and can kill the tree. Complete removal of any diseased tissue is critical. Dip clippers into a 1 part bleach, 9 parts water solution between each cut to prevent reinfection. The final cut should be 8-12 inches below the diseased area. The UC Pest Note on Fire Blight contains photos and more information.