Do not fertilize late in the growing season.Prune out and burn all affected tissues immediately.Maintain adequate spacing between plants and prune to provide good air circulation within the canopy.The handbook also reiterates these cultural controls for treatment: To see photos of this disease, visit OSU Extension's PNW Plant Disease Management Handbook. These spots become black with age and cause death of leaves and young shoots. Bacterial blight (bacterium pseudomonas syringea), also called Lilac Blight. Symptoms are similar to those of winter injury. Bacterial blight starts as brown spots on leaves and stems in the early spring. shrub and as wind-borne travelers, ever seeking new plants to infest. Buds may fail to open or may turn black and die shortly after opening. Flower clusters also may be infected and rapidly blighted and blackened.
Sometimes, several spots will run together, and the leaf may crinkle at the edge or along the mid-vein. Young, infected leaves blacken rapidly starting near the margin and continuing in a wedge-shaped pattern down to the petiole. Infections on mature wood occur only on cherry trees, not on lilacs. Ascochyta blight causes new shoots and flower stalks to wilt and turn brown, encircled by dead areas that have gray to tan, shriveled bases. On young stems, infection spreads around the stem and girdles it so the shoot bends over at the lesion and the parts above it wither and die. Further infectious development depends on the age of the part of the plant attacked. Spots become black and grow rapidly, especially during rainy periods. A yellow halo may also be around the spot. The disease starts as brown spots on stems and leaves of young shoots as they develop in early spring. Spray copper sulfate during the early spring. If your lilac bush does have infection, prune and burn all infected parts as soon as you notice them. The flowers will wilt and turn brown and unopened flower buds become blackened. This pathogen can survive in areas with high humidity and is spread by wind-driven rain or splashing water from irrigation or rainfall.
The dark black streaks on one side of young shoots show the progression of the disease. The main cause of lilac bacterial blight is the bacterium called Pseudomonas syringae pv.
The symptoms of lilac blight are similar in appearance to fire blight in fruit trees.Īt first, leaves look perfectly healthy and then a short time later they look as though someone has placed an open flame near them. The same organism is the source of bacterial blight on pear, blueberry, cherry, maple and many other woody plants. Do new buds and branches on your lilac look blackish, like they've been scorched by a blowtorch? Your bush might have a bacterial plant disease called lilac blight.Ī cool, wet, rainy, spring season favors development of lilac blight, especially if rains follow a late frost or winter injury, according to Oregon State University Extension plant pathologists.Īctually known to scientists by the complete name of "lilac bacterial blight," this disease is caused by the bacterium Pseudomonas syringae pv.
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