U
of I Extension
Sycamore Anthracnose
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[June 11, 2020]
A drive through any town or park in central
Illinois and you will notice that most sycamore trees are void of
any green leaves. So, what is causing this problem?
Anthracnose, which is a disease that thrives with
cool spring temperatures and frequent rains, is most likely the
cause. The spores spread by wind and water to new growth. |
The extent of the disease depends on weather
conditions and the host plant. This has been the perfect spring for
this disease. Most of the infections occur in the two weeks
following bud break. Anthracnose can affect most shade trees, most
often affected in Illinois are ash, dogwood, elm, maple, oak,
sycamore and walnut.
Anthracnose is a common name given to a group of related fungal leaf
and stem diseases. Different fungi produce anthracnose on specific
host plants. The fungi causes tan to brown to black lesions on the
leaves, stems, flowers and fruits of various plants. The color of
the lesions and symptoms of anthracnose vary depending on the tree
species. Infected leaves range from tiny dead spots to large
circular or irregular dead blotches. On sycamore and maple, infected
areas often develop along the leaf veins and midribs, and expand
outward to the leaf edge. This causes the leaf to become distorted.
Heavily infected leaves often curl and drop prematurely, littering
the ground.
![](http://archives.lincolndailynews.com/2020/Jun/11/images/ads/current/graue_preowned_060820.png)
In the early spring, newly emerged leaf tissue of sycamores infected
with cankers will suddenly wilt and turn brown. The fungus grows
from leaf tissue down the leaf petiole and into stem tissue. (Do not
confuse the natural fuzziness of a sycamore leaf with this
infection.) The fungus spores will overwinter within the cankers. In
the spring the spores can reinfect the tree and spread the disease
to other trees. Cankers in branches can girdle and kill the branch.
Twig blight refers to the death of 1 year old twigs. Repeated annual
bud or twig dieback stimulates the development of many short twigs
at the base of the dead twigs given the tree a “witches broom”
appearance.
While this is a common and unsightly shade tree disease, anthracnose
is rarely fatal to a tree. However, repeated infections can weaken
trees. Healthy, vigorous growing trees should quickly recover. An
exception is dogwood anthracnose. This is an aggressive disease that
can cause permanent damage and death of dogwoods. [to top of second
column] |
![](http://archives.lincolndailynews.com/2020/Jun/11/images/ads/current/rohlfs_lda_072017.png)
So what can be done for infected trees?
The first step is to properly identify the problem. A fact sheet on “Anthracnose
diseases of shade trees can be found on the University of Illinois Extension
website at
http://ipm.illinois.edu/diseases/
series600/rpd621/index.html.
Generally fungicides are not recommended except for dogwood
anthracnose. Fungicides must be applied before damage appears and the whole tree
would need treated. This is general cost prohibitive.
The fungus overwinters within fallen leaves and twigs. Therefore, sanitation is
important in minimizing the severity of the disease in the following year. Rake
up and discard fallen leaves and twigs. To prevent reinfection, remove or bury
all diseased plant parts.
Maintain good tree health. Water trees during periods of drought. Supply 1 to 2
inches of water weekly during dry periods. Be sure to apply water slowly and
deeply. Mulch the root zone of the tree with a two to four inch deep layer of an
organic mulch such as wood chips.
Fertilize trees in the late fall to maintain tree vigor. Trees that have severe
anthracnose infection and defoliate early may weaken. Defoliation depletes the
energy reserve of the tree and increases its susceptibility to other pests and
diseases. In addition yearly infections can reduce growth and may predispose the
tree to other stresses.
Make sure trees have proper spacing for good air circulation. Thin out excessive
twig and branch growth.
![](http://archives.lincolndailynews.com/2016/Aug/26/images/ads/current/ldn_business_directory_small2_2016.png)
Sycamore anthracnose can also overwinter in cankers on stems within the tree
canopy. If possible, prune out infected twigs and branch cancers.
If this disease is causing you stress, plant tree varieties that are resistant
to anthracnose.
[Source: Jennifer Fishburn,
University of Illinois Extension, Horticulture Educator] |