The bacteria Erwinia amylovora can infect a pear tree with potentially fatal effects. This bacteria causes the condition known as fire blight, which makes the leaves of the tree appear to have been burnt or scorched. Telltale symptoms of fire blight include blackened, deformed leaves that remain attached to the tree, fruit deformation and oozing from the bark. Insecticides and fungicides are ineffective against Erwinia amylovora -- if your pear tree is infected with this bacteria, all you can do is prune away all infected areas and hope for the best. You should prune 12 inches below the lowest visible infection on the tree. Clean your pruning tools thoroughly before using them on another pear tree, as the bacteria can spread to the healthy tree on the pruning shears. Fire blight affects the entire pear tree; shoots, flowers and fruit all wilt, blacken and die. This disease stays in the limbs of pear trees during the winter time and is transported by rain drops and insects. Warm spring weather and rain and hail cause this disease to grow faster. In order to prevent this disease maintaining trees with protective blossom sprays is the most effective way to treat the fruit. Use fixed copper sanitation if fire blight was in the orchard last year.

http://treefruit.wsu.edu/crop-protection/disease-management/fire-blight/

Fabraea leaf spot, also known as leaf blight and black spot, is caused by the fungus Fabraea maculata. This disease usually appears late in the growing season but can occasionally develop in late May and early June. Fabraea leaf spot attacks leaves, fruit, and twigs of pear. ... Severely infected fruit may also crack.

It could also be pear scab:

https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9003.pdf

Hope this helps!