A rainy summer can leave more than muddy trails in its wake. It can also create favorable conditions for fungal diseases that affect trees.
Maples, in particular, may show signs of tar spot or anthracnose, both of which can cause leaves to brown and drop prematurely. Tar spot appears as raised, black, circular markings, while anthracnose produces dark brown to purplish-black spots that are often irregular and follow leaf veins.
Neither disease is generally cause for alarm in an otherwise healthy maple. Trees typically recover the following spring. Raking and removing fallen leaves — or mulching or composting them — can help reduce fungal spores that could cause another infection.
Oak trees warrant closer attention. The state Department of Environmental Conservation is monitoring a reported case of oak wilt in Greece, N.Y., a non-native fungal disease that can kill red oaks within weeks.
Signs of oak wilt include sudden wilting and leaf drop during summer, browning that begins along the edges of leaves and moves inward, and branches dying from the top of the tree downward. The disease can spread between trees through beetles attracted to fresh pruning wounds and through interconnected root systems.
Because oak wilt can spread quickly, the DEC advises avoiding oak pruning during the spring and summer, when beetles are most active.
New Yorkers who spot possible signs of oak wilt can report them to the DEC Forest Health Research Lab by submitting a report or emailing photos and location information to foresthealth@dec.ny.gov.
For any tree showing signs of declining health beyond seasonal fungal diseases, the DEC recommends consulting a qualified arborist who can assess the tree and determine appropriate care.
If you see signs of oak wilt anywhere in New York, make a report! Submit a report form to DEC’s Forest Health Research Lab or send photos and location information by emailing foresthealth@dec.ny.gov
