Black spots on pear tree leaves
Thank you for attaching the very nice images which permit an easy diagnosis.
The leaves are infected by Fabraea Leaf Spot. ‘Tsu Li’ is very susceptible whereas ‘Kikusui,’ ‘Nijisseiki’ (‘20th Century’), and ‘Shinsui are somewhat more resistant. This fungus disease also occurs on hawthorn, photinia, quince and serviceberry.
This disease develops during cool, moist weather in spring. Heavily infected leaves often drop early. After the weather warms up and dries out, new growth is rarely affected.
Management by home gardeners involves cultural practices, in particular, raking and destroying leaves in the fall. Then, too, avoid overhead irrigation, such as may occur with young trees.