Fungal Infections
Pear tree leaves, fruit, twigs and branches can become infected by fungus. Some of the symptoms of fungal infection are black spots on leaves or stems, early leaf drop or curling and blackening of the leaves. Flyspeck, sooty blotch, fabraea leaf spot and pear scab are all fungal infections commonly affecting pear trees. Prevent fungal infections by removing fallen fruit and leaves promptly, disposing of these away from the pear tree itself. Treat fungal infections with fungicidal sprays. Follow the directions on the fungicide label for correct application.
fabraea leaf spot .... that's my guess ....
"Symptoms & Signs
Fabraea most noticeably first manifests itself as small, purple-black spots on leaves and fruit. Spots gradually enlarge into brown lesions 1/8 to ¼ inch in diameter. When the infection is severe, defoliation can occur and fruit will become deformed and not sellable and/or drop off the tree. Fabraea may also infect shoots, again appearing initially as purplish spots, becoming lesions/cankers which may persist into the next growing season. Leaf and fruit infections are most notable in the Northeast and Midwest, but in the Southeast , shoot infection can be significant. Severe infections can result in reduced flower bud formation for the following season."
"Disease Cycle
Similar to apple scab, much Fabraea overwinters in leaves on the orchard floor. Farther south, overwintering is also likely to occur in shoot cankers. Spores are released from leaves with rain from mid-May to July (in the Northeast and Midwest) and result in primary infection on fruit and foliage. Shoot cankers spread Fabraea from late-April through May (in the Southeast) with more driving rains. Length of wetting for infection to occur can range from 12 hours at 50 degrees F. to as little as 8 hours from 68 to 77 degrees F. Infections take about 7 days to become visible. Once primary infection occurs, secondary infection can spread rapidly with rain and wind during the summer, particularly during wet seasons."
"Chemical Control
Contact/protectant fungicides are necessary to control Fabraea leaf spot. EBDC fungicides (Manzate, Penncozeb, Dithane) and Ziram give good control. (But EBDC’s have a 77 day Pre-Harvest Interval.) Early season fungicide application(s) for pear scab (as long as EBDC’s or Ziram are included) will prevent initial infection by Fabraea. Where disease pressure is high, however, summer-long fungicide applications (once the pear scab season has passed) will be required, particularly in wet summers. Late-maturing varieties may even need fungicide sprays into the early fall to prevent Fabraea from infecting fruit."