COMMON MAPLE PROBLEMS
Why is this topic important?
Is there a optimal time to look for serious problems?
- Maples dominate urban forests (50-90%), so their problems
attract a lot of attention.
- It is important to learn to recognize serious problems, and ignore
What do I look for?
- Yes. Late summer is a good time to view stress in trees because
its effects are so visible in the canopy, and winter is a good time to
see structural defects.
- branch dieback
- early fall coloration
- leaf scorch
- reduced terminal growth
- large seed production
- signs of specific insects or diseases
Bladder gall on maple, a
disfiguring but minor disease
What serious problems can be seen?
What inconsequential problems affect maples?
- Drought - Reduced water supply during summer months means
more water is being given off than is being taken up. Maples will often exhibit
leaf scorch (browning of leaf edges). Repeated leaf scorch often
indicates restriction, smothering, or death of the roots.
- Girdling roots - These roots circle trunks, often below
grade, constricting sugar transport to the roots and slowly killing them.
Norway maples seem particularly prone. Symptoms: center crown death or early
fall coloration. Inspect roots of new stock carefully.
- Included bark - Branch attachments on maples often have
included (embedded) bark between branch and trunk, or co-dominant stems.
This weak union is a common point of failure on older maples. Inspect suspicious
unions showing swelling, plants, or leakage.
- Maple decline - Decline or dieback of sugar maples is becoming
more common. Probable cause is a combination of internal factors aggravated
by environmental conditions. Symptoms: premature fall color, smaller leaves,
and branch dieback. There is no permanent solution.
- Verticillium wilt - This destructive disease attacks through
the roots, causing the xylem to plug up. Symptoms: wilting of leaves on one
limb, reduced growth, gray-green streaks in sapwood. Prune out affected
limbs. Avoid wounding roots, and water new trees. If replacing with another
tree on the same site, select a resistant species.
Where can I get more information?
- Tar spot - This is a fungal leaf disease occurring on Norway,
red and silver maples. Early light yellow-green areas later turn into black,
raised, tar-like spots on upper leaf surfaces. Damage is ugly, but usually
only cosmetic. Raking up and removing infested leaves reduces infection.
- Powdery mildew - Here is another fungal leaf disease. It
shows up as a thin layer or patches of grayish white powdery material. Infected
leaves may turn yellow and drop early. A cosmetic problem only.
- Maple gall mites - These tiny mites produce very visible
warty or spindle shaped galls on the leaves of maples. Usually noticed in
April and May, they can be very unsightly. This is a cosmetic problem that
does not affect the overall health of the tree.
Miller, H. C., and S. B. Silverborg. 1973. Maple Tree Problems.
Syracuse NY: SUNY ESF. (To order, call 315-470-6644) George Hudler,
of maples in eastern North America. For other information,
advice and help on this topic, call offices of your State Urban Forestry
Coordinator or University Extension service, visit urban forestry web sites.