Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001227
11/12/99
QUERCUS DISEASE PROBLEMS
Anthracnose may be a serious problem in wet weather.
Infected leaves have dead areas following the midrib or
larger veins. These light brown blotches may run together
and, in severe cases, cause leaf drop. Trees of low
vigor, repeatedly defoliated, may die. Trees defoliated
several years in a row may need spraying. Apply the first
spray at bud break and make additional sprays at 10 day
intervals if average temperatures are below 55 degrees.
Canker diseases can either attack the trunk or the
branches. Keep trees healthy by regular fertilization.
Prune out diseased or dead branches.
Leaf blister symptoms are round raised areas on the upper
leaf surfaces causing depressions of the same shape and
size on lower leaf surfaces. Infected areas are
yellowish-white to yellowish-brown. The disease is most
serious in wet seasons.
A large number of fungi cause leaf spots but are usually
not serious. Rake up and dispose of infected leaves.
Chemical controls are usually not warranted.
Powdery mildew (Vis. 2) coats leaves with white powdery
growth. Spraying may not be needed.
Oak wilt is a fatal disease beginning with a slight
crinkling and paling of the leaves. This is followed by
leaf wilting and browning of leaf margins then working
inward. The symptoms move down branches toward the center
of the tree. Cut down and destroy infected trees. The
disease may be spread by insects or pruning tools.
Shoestring root rot attacks the roots and once inside
moves upward, killing the cambium. The leaves are small,
pale or yellowed and fall early. There is no practical
control. Healthy trees may be less likely to be infected
than trees of low vigor.
Chlorosis (Vis. 1) due to iron deficiency occurs on high pH
soil. Sulfur will increase soil acidity. Trunk implants of
plastic capsules containing a soluble iron source may
overcome deficiency symptoms until the soil conditions are
corrected.
Related information.
Pesticide Recommendations
Anthracnose
Oak Wilt
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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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