What’s Wrong With My Mountain Laurel?

Are the leaves yellow with green veins?

Did the leaves turned brown during winter?

Do the leaves have yellow, brown, or black spots?

Are there any large, circular, brown lesions on leaves?

Are the leaves pale and mottled?

Are the leaves yellow and wilting, branches may drop off?

Does the plant begins to wilt and are there zigzag paths in roots or stems?

When acid-loving plants are in soil that is too alkaline they develop a condition called chlorosis. The yellowing of their foliage is a signal that they need more acid in their soil. This sometimes happens when shrubs are planted near masonry walls and over time the rain leaches lime from the mortar into the soil. To acidify the soil, add peat moss or aluminum sulfate to it. Do not use lime near mountain laurels.

Mountain laurels that are exposed to bright winter sunlight and harsh winds often develop winter burn on their foliage. Their leaves dry out, turn brown, and will eventually drop. Spray foliage with anti-transpirant just before cold weather sets in and shield exposed shrubs with a burlap windscreen.

Your plants might be suffering from a fungal leaf spot disease. Spots may enlarge rapidly, especially in wet weather. Destroy infected leaves or plants. Spray plants with sulfur to prevent the disease from spreading, especially if the weather is wet. Prevent problems by thinning plants to provide good air circulation.

Leaf blight in mountain laurel is caused by fungus Diaporthe kalmiae (Phomopsis kalmiae). Prune away and destroy affected foliage and branches. The lesions frequently first appear near the margin or tip of the leaf, gradually enlarge, merge with other lesions, and result in the death of the entire leaf blade. Dead or diseased leaves should be removed from the bushes and soil surfaces and destroyed by composting or burning.

Lace bugs are flat, dark-colored insects with lacelike wings that feed on the undersides of leaves. They cause leaves to turn yellow, then brown, and eventually die. Treat plants with a commercial pyrethrin spray or dust if the damage is severe. Prevent problems by covering plants with row cover until they blossom.

These problems are caused by Rhododendron borers. These small, clear-winged, wasplike moths lay eggs on leaves, twigs, and bark. Their larvae burrow into the weakened stems and branches. Control borers by pruning and destroying affected branches. Seal the cut branches with putty or grafting wax.

These symptoms are caused by Black vine weevil larvae. The larvae are small whitish grubs, which feed on roots deep in the soil. The larvae feed on the roots and stems. The feeding can girdle the stem, killing the plant. Drench the soil around your mountain laurel with the predatory nematodes solution. If there are adult weevils, knock them from the plant on a piece of cloth and destroy them.

If the leaves are curling downward followed by the appearance of a circular canker on the branch your plant is suffering from Botryosphaeria canker. This disease infects one branch at a time. On a dry day, prune out any infected branches and then burn them. Remove the branch about 6-8 inches beneath the canker. Sanitize your pruning shears with a 10% bleach solution between each cut.