Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001425
11/12/99
SYRINGA DISEASE PROBLEMS
Bacterial blight is most serious on white flowered
varieties. The young shoots develop black stripes or one
side of the shoot turns black. Spots develop on the
leaves, forming a water-soaked blotch. Young leaves turn
black and die quickly. On older shoots, the spots enlarge
more slowly. The flowers wilt and darken. The disease is
worse when wet weather occurs as the new shoots are
developing. Thin plants to increase air circulation.
Remove and destroy diseased shoots and avoid excessive
nitrogen fertilizer.
Phytophthora blight kills stems to the ground. The
leaves turn black and shoots have brown lesions on them.
Leaf blotch causes zoned, brown spots. The infected
area drops out, leaving a hole in the leaf.
Many fungi cause leaf spots.
Powdery mildew coats the leaves (Vis. 1) with white powder.
During wet weather, lilacs mildew easily. Mildew is
especially severe on shade-grown plants. Ignore late
season infections.
Verticillium wilt causes wilting and premature leaf
drop. The disease may kill one, several or all the
branches. There is no chemical control.
Bacterial crown gall causes round, warty galls on the
stems near the soil line. There is no chemical control.
Remove infected plants and do not replant in the same
spot.
Related information.
Pesticide Recommendations
Bacterial Blights
Powdery Mildew
Verticillium Wilt
Bacterial Crown Gall
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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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