Weather related disease problem on sycamore trees

The extra rain and cool weather we’ve been getting has been a mixed blessing. It’s June and a lot of gardens, farms and fields haven’t been planted yet because of saturated soil and cool temperatures.

On the other hand it has been great for established plants like trees and shrubs. In most cases they’ve made tremendous growth except for one notable exception — sycamore trees.

It’s quite startling to see how little progress the sycamore trees in our area have made. Most of them have very few leaves on them at all.

The maple tree on the left is flush with new leaves while the sycamore on the right is nearly bare.

This is due to a disease called anthracnose, a fungal malady of sycamores that is present in varying degrees from year to year. This year’s outbreak is particularly severe due to unusual weather.

A lot of it has to do with timing. Rainy and cool conditions that occur a couple of weeks after bud break allows the anthracnose fungus to thrive. The longer that type of weather stays around, the worse the infection gets. That’s why our sycamores are looking so bad for so long this year.

There’s really nothing practicable we can do to cure or even prevent this disease.

Young leaves killed by anthracnose.

Fortunately, once it gets warmer and drier they’ll bounce right back. Most of the time, very little major damage is done to the trees. The most obvious permanent damage you’ll see is “witch’s broom” a disfigurement of the branches that occurs in the spot the fungus killed twigs. At that point several small branches will grow from a single point giving it the typical witch’s broom appearance. Once the leaves fill out, however, the disfigurement is not so noticeable.

Witch’s broom caused by anthracnose.

Dead twigs eventually fall to the ground and can cause a mess in the lawn. This is probably why some people think of sycamores as messy tree, but it’s not the poor tree’s fault.

Trees can be sprayed or treated but it really doesn’t do much good since the infected parts can’t be healed anyway. Waiting for the weather is the best course of action in most cases. It extremely rare for a tree to die from anthracnose unless it is under stress from something else such as being planted in the wrong area or has a lot of bark damage from lawn mowers.

A little bit of fertilizer may help your tree to grow back its leaves faster. Generally, trees growing in lawns will get the nitrogen they need from the fertilizer used to fertilize the grass.

Anthracnose will always be with us so it’s just something we’ll have to live with.

Bob