This is soon followed by leaf and shoot discoloration and necrosis which proceeds down the shoot. Infections of short shoots likely to lead to canker development on the supporting limb. The rate of disease spread into the tree from infected shoots is dependent on temperature and tree defense responses which vary with variety and tree vigor. Canker blight symptoms are often mistaken for shoot blight, but close examination will show its relation to a nearby canker and different symptom patterns. Streptomycin used at bloom, and cooper used at green tip, reduce inoculum for shoot tip infection, but are not effective for controlling fire blight in the shoots after petal fall.
Growers can spread the disease through pruning and general cultural activities.
Preventing fire blighted shoots in the orchard . The adequate control of fire blight in a severe disease year is difficult to attain. While trees were dormant, blighted twigs should have been pruned just below the infected areas and destroyed. This annual pruning must be done carefully, so that all infected branches are removed. It is not necessary to sterilize pruning tools for dormant pruning.