Identifying and Managing Sycamore Blight on Sycamore Trees
Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent
Do you want the good
news of the bad news first? The bad news is that many of our area sycamores are
infected with sycamore blight this spring.
The good news is that sycamore blight seldom kills a tree.
Well, it's good news for those of you who like sycamore trees.
Most of you know that sycamores are not my favorite type of tree. One reason that sycamores don't hold my esteem is that they
get sycamore anthracnose .
Sycamore anthracnose,
also know as sycamore "blight", is a fungus disease which commonly
attacks the leaves and twigs of sycamore trees.
The cool, wet weather this spring has been ideal for the development of
this disease. The fungus survives
the winter in cankers (which look like small wounds) on the branch twigs and
also on fallen leaves and twigs. During
cool (55 degrees Fahrenheit), wet spring weather, the spores of the fungus
develop in these cankers. The
spores are blown and splashed by the rain onto newly expanding buds, shoots, and
leaves. The spores germinate and the fungus infects and kills plant tissue.
The first symptom of
sycamore blight is usually sudden browning and death of single leaves or
clusters of leaves as they're expanding in the spring. It’s easily mistaken
for frost or wind injury.
A quick look around
the area, and you’ll easily find a large number of sycamore trees that are
quite sparse and appear to be leafing out very slowly.
Many of these are affected by “blight.”
As our weather turns warmer (hopefully), the trees will form new leaves
but the foliage will not be as dense as in other years.
If our cool and wet
weather persists, later leaf infections may also occur.
Symptoms of these later infections appear as brown dead spots which start
at the base of the leaf or at a vein
on the leaf. The brown spots then follow the veins outward.
Control of anthracnose
on susceptible trees is difficult, mainly because of the large size of
most sycamores. Recommended
cultural control consists pruning off and destroying infected twigs and dead
branches and also raking up and disposing of all the fallen leaves and dead
twigs. Both of these actions are designed to remove the organism
that lives through the winter and produces spores the next spring.
Spraying with a
fungicide to protect expanding buds and leaves from the fungus can be done in
the spring as the buds begin to swell and just
start to break open. This is most
practical where trees are young and small enough for you to be able to achieve
good coverage when spraying. Adequate
coverage is difficult to achieve on large trees, even for competent applicators
with good equipment. Recommended
fungicides are applied at bud‑break and then again at ten to fourteen day
intervals during periods of wet weather. Remember that good coverage is
essential for effective control.