Bacterial leaf scorch, not antracnose is the killer of sycamore trees.

Antracnose is a fungal disease that attacks and turns sycamore leaves brown, remaining on the tree. Not fatal. The disease that is actually fatal on sycamore trees is bacterial leaf scorch. Spray Garrett Juice plus garlic tea on emerging new foliage in early spring.

Apply The Sick Treatment. Sprays of  potassium bicarbonate, garlic and neem are also effective. Avoiding planting sycamores is the best control. It also attacks beans and ornamentals. The foliage turns a tan color overnight. Control is difficult other than by avoiding the use of susceptible plants. Baking soda or potassium bicarbonate sprayed as leaves emerge in the spring will sometimes help.
 
Best cure is soil improvement and selection of adapted plants. Also called bird’s-eye spot, it is a fungal disease that causes small dead spots with a raised border, sunken center, and concentric rings of pink and brown. There may be other typical symptoms. Symptoms of bean anthracnose manifest on the pods as circular, black, sunken spots that may ooze pink slime and develop red borders as they age. To control thoroughly compost infected plants, and avoid touching wet plants and spreading the disease.