How to Troubleshoot a Diseased Lilac Bush

lilac image by Henryk Olszewski from

As one of the most fragrant flowering shrubs, gardeners throughout the United States enjoy lilacs, and they can choose from 28 species of the plant and over 100 different crossbreeds, according to Washington State University. Lilacs are durable and reliable plants that are able to withstand winter temperatures of up to 10 degrees C below zero. However, when affected by drought or poor nutrients, these shrubs can succumb to disease. Learning how to troubleshoot common lilac diseases will aid you in caring for your lilac bush.

Examine the leaves of the shrub. Damage with brown spots along the margins and central vein points to lilac blight, while discolouration along the veins and edges points to leaf scorch and holes or tatters points to leaf tatter. Yellowing of new foliage indicates micronutrient chlorosis, which is a lack of a needed nutrient.

Look at the bark on the bush. Splitting bark is rarely serious, although it can allow disease organisms into the plant, but diffuse or target-shaped cankers can be lethal.

Inspect the lilac bush for signs of powdery mildew, a fungus that appears like a dusty white or grey coating on the leaf and trunk. Powdery mildew comes off slightly if you rub the infected area, and it usually has a circular pattern.

Search for any sooty mould, which appears as a heavy coat of black mould on branches of the tree.

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