Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00000036
11/12/99
ACER DISEASE PROBLEMS
Anthracnose, caused by the fungus Gloeosporium apocryptum,
is more of a problem in rainy seasons. The disease
resembles, and may be confused with, a physiological
problem called scorch. The disease causes light brown or
tan areas on the leaves (Vis. 4). Anthracnose may be
controlled by fungicides sprayed on as leaves open in the
spring. Two additional sprays at 2 week intervals will be
needed. The disease is most common on Sugar and Silver
Maples and Boxelder. Other maples may not be affected as
severely. Sprays may need to be applied by a commercial
applicator having proper spray equipment.
Verticillium wilt symptoms are wilting and death of
branches in the tree crown. Infected sapwood will be
stained a dark or olive green but staining can't always be
found. If staining can not be found do not assume the
problem is not verticillium wilt. Severely infected trees
probably can't be saved. Lightly infected trees showing
only a few wilted branches may be pulled through. Girdling
roots will cause symptoms which mimic verticillium wilt.
Girdling roots grow around the base of the trunk rather
than growing away from it. As both root and trunk
increase in size, the root chokes the trunk. Girdling
roots are detected by examining the base of the trunk.
The lack of trunk flare at ground level is a symptom. The
portion of the trunk above a girdling root does not grow
as rapidly as the rest so may be slightly depressed. The
offending root may be on the surface or may be just below
the sod. The tree crown (Vis. 1) shows premature fall
coloration and death of parts of the tree in more serious
cases. If large portions of the tree have died it may not
be worth saving. Girdling roots are functional roots so
when removed a portion of the tree may die. When the
girdling root is large the treatment is as harmful as the
problem. After root removal, follow up treatment includes
fertilization, and watering during dry weather.
Scorch occurs during periods of high temperatures
accompanied by wind. Trees with diseased or inadequate
root systems will also show scorching. When trees do not
get enough water they scorch. Scorch symptoms are light
brown or tan dead areas between leaf veins. The symptoms
are on all parts of the tree or only on the side exposed
to sun and wind. Scorching due to dry soil may be overcome
by watering. If scorching is due to an inadequate or
diseased root system, watering will have no effect.
Nutrient deficiency symptoms are yellow or yellowish-green
leaves with darker green veins (Vis. 3). The most commonly
deficient nutrient on maple is manganese (Vis. 2).
Implanting capsules containing a manganese source in the
trunk will alleviate the symptoms. Test soil samples to
determine if the soil pH is too high for best manganese
availability. Plants exposed to weed killers may also show
similar symptoms.
Related information.
Pesticide Recommendations
Anthracnose
Verticillium Wilt
Cankers
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to commercial products or trade names does not imply
endorsement by MSU Extension or bias against those not
mentioned. This information becomes public property upon
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This file was generated from data base ZZ on 01/19/00.
Data base ZZ was last revised on 11/12/99.
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