Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00000078
11/12/99
ALCEA DISEASE PROBLEMS
Anthracnose attacks the stems and invades the roots.
Seedlings are most susceptible and high temperatures and
humidity favor disease development. The leaf spotting is
most common on greenhouse grown seedlings.
Rust infects leaves, stems, bracts and other green plant
parts. Brown pinhead size spots develop on the undersides
of leaves. On the upper leaf surface the spots are
larger, bright yellow or orange with reddish centers.
The spots run together causing death of large leaf areas.
Ash gray pustules form on the lower leaf surfaces during
rainy weather. Remove infected leaves when first noticed.
Destroy old plant parts at the end of the growing season.
Leaf spot causes angular grayish spots scattered over the
leaf. The dead tissue falls out giving a shothole effect.
Remove and destroy plant residues at the end of the
growing season.
Powdery mildew covers the leaves with a white powdery
growth.
Related information.
Pesticide Recommendations
Hollyhock Rust
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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