It causes bright orange swollen spots on the leaves, petioles and green stems of buckthorns. Buckthorns are the alternate host for oat and rye crown rust but the rust may attack a wide range of other grasses. No treatment is recommended. Clean harvesting of all ripe fruit will greatly help to reduce problems with botrytis gray mold. This very common fungal disease grows rapidly on over-ripe or damaged fruit and can quickly infest an entire fruit cluster under moist conditions.
Symptoms are numerous, small, raised, rust-colored spots on the leaves.
Thorough cleanup of old plant debris in the fall helps to reduce the disease next season. Fungicide treatment now would be of little value. Like ash anthracnose, it causes fairly large, irregularly shaped brownish spots, typically along the margin of the leaf. However, these infected maple trees will generally not drop as many leaves as ash trees do when they are infected. Control strategies are similar to that of ash so treatment now is probably not going to be very effective.