Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001305
11/12/99
SALIX DISEASE PROBLEMS
Crown gall causes galls to form near the soil line or
farther up the plant. Take out infected plants and do not
replant in the same area for at least 2 years.
Willow scab attacks and kills young leaves within a
very short time. The fungus enters twigs, kills back the
young shoots and causes cankers. Olive green spore masses
can be seen along the veins on the undersides of leaves.
Another fungus, Physalospora miyabeana attacks willow and
the two fungi in combination cause willow blight. Prune
out infected branches and use resistant species.
Black canker is caused by Physalospora miyabeana and is
one of two fungi in the willow blight complex. Black
canker causes dark brown spots on the leaves. Whitish
gray lesions with black borders appear on the twigs and
stems. Prune out infected branches and use resistant
species. Weeping willow appears to be resistant.
Many fungi cause cankers on willow and infected branches
are pruned out. If the trunk is infected and girdled, the
tree will die. Keep trees healthy by regular
fertilization.
Many fungi cause leaf spots but are not serious enough to
warrant preventive sprays. Rake up the fallen diseased
leaves in the fall.
Powdery mildew causes a white coating on the leaves.
The disease is usually not serious.
Rust causes yellow spots on the lower surface of leaves
and, if severe, defoliation. Chemical controls are
usually not needed. Rake up and destroy leaves from
diseased trees.
Tar spot causes black, raised spots on leaves. Rake up
and dispose of fallen leaves from diseased trees at the
end of the growing season.
Related information.
Pesticide Recommendations
Bacterial Crown Gall
Cankers
Powdery Mildew
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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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