Lilac bush problems can stress out even the most seasoned gardeners. These treasured shrubs bring a brilliant abundance of anxiously awaited, intensely fragrant flowers for only a short period of time in the spring. Losing a lilac bush is a sad day for an avid gardener. Watch out for bacterial blight, bark splitting and damage from pesticides and fertilisers.
A bacterium called pseudomonas syringae pv. syringae is the cause of lilac bacterial blight. All varieties of lilacs are vulnerable to this disease. Drought-stricken, wounded and improperly fertilised lilac bushes are more susceptible. Brown spots which may enlarge appear on the leaves and stems, eventually killing the foliage, shoots and blossoms. A healthy plant has the best chance of resisting bacterial blight and other lilac bush problems. The Plant Clinic at Cornell University encourages proper spacing of plants and advises to "avoid wetting the foliage and overhead irrigation to minimise splashing of the bacterium on to the host plants. Prune plants to allow for increased air circulation through the canopy." Some varieties that are resistant to this lilac bush problem are wonderblue, burgundy queen and royal purple.
Bark splitting can occur at any time of the year on any part of the lilac bush that is covered in bark. Environmental factors such as repeated freezing and thawing can cause a type of bark splitting called "frost cracks." A bark split is not likely to kill your lilac bush, but it is an entry point for diseases that can be fatal. Research cited by the Plant Clinic at Cornell University says that trees are capable of healing themselves, and tree wound paints should not be used. Instead, using a sterile and sharp knife, cut a ring around the wounded area about three-quarters of an inch away from the edge of the wound. Remove the bark from around the wound and leave the area bare and untreated. Fertilise as usual in the spring, and provide adequate irrigation (do not overwater) until the tree heals itself. Use this same protocol for minor mechanical damage from lawnmowers or other machinery.
Damage from Pesticides and Fertilizers
Applying fertilisers can damage rather than help your garden plants. A shrub without lilac bush problems is healthy and does not have a nutrient deficiency. Adding fertiliser where none is needed causes an imbalance of nutrients, rendering the plant subject to lilac bush problems.
Leaf burn is an obvious symptom of the overapplication of pesticides and fertilisers. The foliage will exhibit abnormalities on the surface area over which the treatments were applied. It is common to see white blotches and spots. To minimise the damage, rinse the plants with a garden hose as soon as you notice the spots. If the plant remains healthy, and there is enough time left in the growing season, the lilac bush will replace the leaves with healthy ones.