Your pear tree possibly has a bacterial disease called fire blight.  Fire blight is one of the most destructive diseases of apple and pear trees.  Cool wet springs are the ideal conditions for this pathogen to spread.  Fire blight primarily infects blossoms in spring time, and is spread primarily by insects but also by wind and rain.  Spring symptoms include blackening on leaves, petioles and stems.  The summer symptom that you see show up as dead brown foliage on entire branches, with the tips curving downward forming a shephard’s hook.  Eventually, the pathogen moves down into the branch and forms cankers, which are sunken, dead areas of bark.  Bacteria can sometimes be seen oozing out of a canker, especially in spring. 

Homeowners can manage this disease using cultural practices.  In winter or early spring, prune out all dead wood and remove it from your property.  Prune out infections 8-12 inches below the diseased tissue and sterilize your pruning equipment between each cut with a 10% bleach solution or alcohol.  In spring, scout for symptoms and prune out infected twigs and flowers as early as possible.  If necessary, apply a copper spray when at ½” green tip. Follow the application guidelines on the pesticide label.