Fire blight is a bacterial disease that is common in pears and other members of the rose family.
Since this is a bacterial disease, it is hard to combat. At this time, the only option is to carefully prune out all the blighted stems and tissue. It is very important to prune well below the the diseased portion of the branch. It is also very important to disinfect your shears or pruning saw in between each pruning cut. Dip them in a 10% bleach solution to disinfect.
Here is a link that gives specifics on pruning out fire blight.
Once you have correctly pruned out all the blighted stems and tissue, you won't need to do anything until next spring.
In the spring during flowering and according to the label directions, spray with Agri-Mycin 17 Fungicide if you can get it or with Bonide Liquid Copper Fungicide according to the label directions if Agri-Mycin isn't available.
- The blossoms must be sprayed because the bacteria usually enters through the flower and infects the wood. As you will see when you read the label, it will take several applications of either product to help control the fire blight.
Trees are infected from other nearby trees that have fire blight cankers already so unless your treat them in the spring, your carefully pruned trees will be reinfected each spring from the neighborhood trees.
Be sure to check your trees carefully for signs of the fire blight canker and do some careful pruning if you see any.
If the trees do not recover, consider replacing them with varieties that are resistant to fire blight.