Diseases of the California Sycamore Tree

Many of the largest tree species native to California are conifers, but there are a few big broadleaf species that also call the Sunshine State home. The California sycamore (Platanus racemosa) is an excellent example, as it not only reaches heights in excess of 80 feet, but it has some of the largest leaves of any tree native to the U.S.

California sycamores grow wild along the southeastern coast of the state, but they’re often planted by homeowners, landscapers, and commercial property managers, so you can see them just about anywhere. It’s easy to understand their popularity: They often exhibit attractive fall color, and they have some of the most attractive tree bark around.

But unfortunately, despite all of these characteristics that make California sycamores so popular, they’re also susceptible to a few diseases. We’ll explain a few of the most noteworthy diseases that afflict these trees, so you can keep an eye out for the first signs of illness and get your trees the prompt care they need.

Sycamore Anthracnose

Sycamore anthracnose is one of the most common diseases that commonly affect California sycamore trees. It can be very difficult to treat, but it doesn’t typically kill mature, established trees.

A fungal disease, sycamore anthracnose typically affects the young shoots and leaves of a tree. You may see black or brown lesions appear on the surface of the leaves, some of the branches may become twisted or deformed, or you may notice your tree shedding leaves during the early summer. In some cases, you may see portions of the canopy defoliate completely.

Sycamore anthracnose is most commonly observed following wet springs. The ample moisture gives the fungus a chance to disperse, and the new leaves provide an easy and readily available food source for the fungus (mature leaves typically manage to fight off infection more effectively than young leaves do).

Sycamore Canker Stain

Sycamore canker stain is a fungal disease that affects sycamores and London plane trees in California. Another serious ailment, this disease often causes trees to die within about 24 months of the first visible symptoms.

Some of the most reliable signs of infection include small, yellow leaves throughout the canopy and the presence of depressed cankers on the trunk and primary branches. The wood of infected trees is often discolored, yet it doesn’t become soft or rot away as happens with some other canker diseases.

Leaf Spot Disease

Unlike sycamore anthracnose and canker stain, which primarily affect sycamore trees, leaf spot disease is caused by more open-minded pathogens (fungi). The exact nature of the illness caused will vary based on which fungi is attacking a given tree, but most produce relatively similar symptoms: Numerous yellow to brown spots appearing on the leaves.

Powdery Mildew

Like leaf spot disease, powdery mildew affects many different species; it isn’t a particularly specific pathogen. Characterized by the presence of a white, powdery substance on the leaves and new shoots, powdery mildew usually kills the leaves it infects.


If you suspect that your sycamore tree is suffering from a disease or is simply not thriving the way you’d like it to, give your friends at Evergreen Arborist Consultants a call. We’ll have one of our ISA-certified arborists visit your property, inspect the tree in question, and then provide a recommended course of action.

Just be sure to do so promptly to give your trees the best possible chance at a recovery.