Why is my sycamore tree dropping its leaves?
The leaf drop is likely due to anthracnose. Anthracnose is a common fungal disease of sycamore, ash, maple, oak, and other trees. Anthracnose is most severe in years with cool, wet spring weather. While anthracnose may cause extensive defoliation, it does not cause serious harm to healthy, well-established trees.
Symptoms of anthracnose on sycamores include brown blotches on leaves, death of young buds and shoots, and leaf drop. In cool, wet springs, affected sycamores may lose most of their initial foliage.
Fortunately, the sycamore trees will continue to produce additional leaves and shoots through early summer. Foliage that develops in late spring and early summer shouldn’t become infected as warmer, drier weather suppresses anthracnose. Most sycamores should have a good canopy of leaves by late June or early July.
Since anthracnose does not cause serious harm to sycamores, fungicide treatments are rarely warranted.