Description
Sycamore anthracnose is a fungus (Gnomonia leptostyla) and
is one of the most serious diseases of Sycamore in the US. The most
conspicuous symptom of the disease in early spring is death of twigs
and new shoots. Repeated killing of young twigs results in abnormal
branching and gives the tree a ragged appearance. After bud break,
sycamores show a scorching and wilting of new shoots and leaves.
Later, fully expanded leaves develop elongated tan to brown lesions
parallel with the midrib and veins.
Key Distinctions
There are 4 stages of the disease.
Leaf Infection, Twig Blight, Bud Blight,
and Shoot Blight.
The fungus that causes Sycamore Anthracnose spends most of it’s
life cycle alive on the 1 - 2 year old twigs in the crown of the
tree, creating cankers. These cankers are the source of all future
disease infections. The fungus grows inside the twig causing injury
to the tree including shoot blight, bud blight and twig blight.
The fungus also produces small black fruiting structures, which
break through the bark and cast spores that cause leaf infection
and reinfection of the new growth.
Severity of the disease is related to average temperature in the
spring – NOT WETNESS. Temperatures averaging between 50 and 55 degrees
fahrenheit as the buds break cause the most severe infections. Temperatures
averaging above 55 degrees create conditions that produce less severe
tree injury.
The leaf infection stage is caused by a spore which lands on the
leaf and germinates. This is the only stage of the disease that
requires moisture. It is also the least damaging to the tree as
it causes leaf blotching. This is how Sycamore Anthracnose creates
new infections. The spore infects the leaf, grows into the vein,
down the petiole and into the new twig, where it remains until the
next season.
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The severity of Sycamore Anthracnose
in the spring is influenced by temperature – Not wetness during
leaf development |
Leaf infection creates small blotches
that collate into the veins – it grows down the petiole and
into the twig. |
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