Question: Isolated branches of my photinias have died suddenly. What should I do to keep the problem from spreading?
Answer: That sounds like fire blight, the bacterial problem of the rose family. Affected leaves will remain attached to the stems for many months. Prune to remove the dead wood, cutting back into healthy tissues by several inches. Disinfect your pruning tools by dipping them in a 10-percent chlorine bleach solution between each cut. Spray while the plants are in full flower with agricultural streptomycin.