The sycamore is a fast-growing, popular tree that can grow 100 feet or higher. It has a wide spread when mature, providing shade to the people and plants beneath it. Sycamores grow best in moist soil, so they do well when planted near water. They also prefer an acidic pH. The American sycamore is susceptible to a disease called anthracnose, which can cause widespread problems. The London and Oriental varieties are more resistant to disease.
Examine the tree to determine exactly where it is damaged. Look over the bark and leaves to see if the spots or holes are affecting one part and not the other. Take a look around the tree, as well, to see if nearby plants are damaged. This would indicate an environmental cause. If you live in a coastal area, salt spray could be making the sycamore sick. In this case, put up a plastic barrier to prevent further damage.
Rule out frost damage. If you notice leaves are turning brown or the wood is splitting in early spring, it's very likely because of a cold winter. In this case, protect the tree during harsh weather with tarps and landscape cloth.
Look for signs of anthracnose, which is a group of fungal diseases that affect sycamore, hickory and maple trees. The disease causes extensive defoliation, the leaves and twigs will unfold, shoots die and older leaves turn brown.
Check out the main vein in the leaves to see if there are black or brown areas. The twigs may also be growing in a crooked fashion, or have cankers along them. These are also symptoms of anthracnose.
Trim infected branches and twigs. Cut them off where they meet healthy wood. Take all the infected cuttings away from the area so they don't infect other parts of the sycamore.
Spray a pre-emergent fungicide when the buds start to grow in the spring. This is a good preventative measure if you've dealt with anthracnose before. The goal is to apply the chemical before the fungus grows spores. Follow the instructions on the label.
Reapply the fungicide every week or two whenever the average temperature is below 60 degrees Fahrenheit. This is prime time for the threat of anthracnose. Once it gets warmer outside, anthracnose diminishes as a threat.
Watch for moist weather in mid-summer. If the sycamore is growing a second set of leaves at this point, the disease may return. Reapply the fungicide.