BACTERIAL BLIGHT OF LILAC
|Bacterial blight of lilac|
Photo: U of MN Extension Service
Bacterial blight of lilac, also known as blossom blight or shoot blight, is caused by the bacterium Pseudomonas syringae pv. syringae. Chinese, Japanese, Persian, and common lilac are all affected, with white flowering varieties being the most susceptible. Bacterial blight can easily be mistaken for freezing injury from late spring frosts.
The bacterium survives winter in cankers, plant debris, weeds, and soil. The bacterium may also be present on healthy plant tissue year round without causing disease. Bacterial blight can be spread by insects, pruning tools, rain, and wind.
Infection starts on the newest growth in the spring, during rainy weather. Early symptoms may include dark brown spots with yellow halos, dark brown blotches starting at the leaf margins and advancing inward, blackened shoots, and black streaking on twigs. Leaf spots may coalesce, resulting in shriveling and death of leaves. Shoots may be girdled, causing death of leaves and blossoms.
Stress or injury resulting from poor or improper nutrition, frost damage, or wounding can predispose plants to bacterial infection. Control of this disease can be achieved through the following practices:
Chad Behrendt, Crystal Floyd