Diseases of the Cherry Laurel

Cherry laurel (Prunus laurocerasus), sometimes called English laurel, grows well in U.S. Department of Agriculture plant hardiness zones 6 through 8. A versatile shrub, it can be grown as a hedge, natural privacy screen or as a bedding plant. It has leaves that stay green year round and aromatic flowers that give way to tiny, cherry-like fruit sought after by birds but not palatable to humans. This sprawling shrub is the least susceptible to diseases of the Prunus species, but when not planted in well-draining soils it can have problems.

If the leaves of your cherry laurel look like someone shot them with a BB gun, the tree may be suffering from shot-hole disease. This disease has a fungal and bacterial form. The fungal form overwinters in cracks on branches or lesions in buds and leaves. When it rains, fungi are dispersed onto young leaves where they eventually form brown spots. Over time, the centers of these spots fall out, leaving irregular holes. The bacterial form of shot-hole disease is also dispersed when it rains. The bacteria enter wounds on the leaf, forming brown lesions with yellow halos, and eventually the centers fall out. Affected leaves will continue to grow, but if they are too unsightly, you can prune away a few of the leaves without stressing the plant. Disinfect pruners to avoid spreading the disease.

Many species of plants are susceptible to powdery mildew, and cherry laurel is no exception. The disease starts as a white powder-like substance on either upper or lower portions of the leaves. Over time, the white area will turn brown and die, leaving irregular-shaped holes in the leaf. Affected edges appear jagged as if damaged from chewing insects. Powdery mildew is caused by airborne fungi that overwinter on leaves on the shrub or fallen leaves. Mildew usually clears up when the weather becomes drier.

Root rot is caused by microscopic pathogens that thrive in poorly draining soils. They interfere with the shrub’s ability to take up water and nutrients. Affected laurels look wilted even though the soil is saturated. They have discolored leaves and experience premature leaf drop. There is no cure for root rot in cherry laurel. If your plant is affected, it should be dug up and destroyed. The soil should be replaced with fresh, clean soil, after digging out all soil in the root area and disposing of it.

Many cherry laurel diseases can be avoided by taking a few precautionary steps. Since many disease are caused by wind-driven rain, don’t water from overhead. Clean up infected fallen leaves; bag and dispose of them in the trash to prevent overwintering of disease-causing spores and bacteria. In cooler growing zones, plant cherry laurel in full sun. Many fungi prefer shady locations and cooler temperatures; planting in the sun increases the temperature and helps soil dry out periodically. To prevent root rot, plant in well-draining soil and only water when the top 3 inches of soil is dry to the touch.