Fire blight is an infectious bacterium that if left untreated will destroy an entire tree. According to Colorado State University, fire blight affects members of the rose family, including apple and pear trees, and is characterized by dead and dying branches, black spots, blackened leaves and oozing cankers. Treating fire blight is accomplished with pruning and the application of a white vinegar solution to create an acidic environment that the bacteria will find inhospitable.
Examine the tree for any twigs or branches that are affected by the fire blight.
Cut the branches and twigs at least 8 to 12 inches below the affected area or canker with a pair of sharp pruning shears.
Prepare a mixture of one part white vinegar and one part water in a plastic spray bottle.
Spray the cut with a healthy coating of the mixture. This mixture will create an unfavorable environment that will help prevent the fire blight from spreading.
Continue to monitor the tree and each time a new canker or affected area emerges, treat it in the same manner.