Diseases of the cherry laurel shrub (Prunus laurocerasus), also referred to as English laurel, generally consist of fungal infections and illness due to incorrect watering. Cherry laurels thrive in moist, well-drained soil and full sun to partial shade; maintain your cherry laurel plant to keep it vigorous and less susceptible to disease.
Since cherry laurel shrubs prefer well-drained soil, planting them in sites that are excessively wet leaves them vulnerable to root rot. Caused by a fungus called Phytopthora cinnamomi, the infection affects the root systems of plants, causing rot and decay of plant tissue and the destruction of roots. Nutrients and water run from roots to leaves, so the normal flow of natural life-support to the shrub ends, leading to diminished health and eventual death of the cherry laurel. For control, choose resistant plant varieties, or apply the fungicide methyl bromide (contact a professional) for existing infection. The fungicides fosetyl-Al or metalaxyl are appropriate for home use but may only decrease fungus without curing the disease, explains the NC State University Cooperative Extension Service.
Shot hole is a disease affecting cherry laurels that is both bacterial and fungal in nature. This infection is created by the bacterium Xanthomonas prunii and the fungus Blumeriella gaapi or Cercospora sp. This infectious disease causes symptoms that begin as red or purple spots on the surface of leaves; the spots dry out and the tissue disintegrates, leaving holes that appear to have been created by a shotgun. As more holes develop, their borders meet, and more expansive holes form until leaves completely drop and the laurel is severely ill. Overhead watering may promote greater vulnerability to infection. For control, remove and destroy infected plant parts that have fallen from the plant. Also, apply a fungicide with the active ingredient mancozeb as soon as symptoms appear, as recommended by the Cobb County Extension Service.
Botryosphaeria infection attacks stressed plants, including cherry laurel shrubs. This infectious fungus causes limb dieback on cherry laurels; though the plant may appear to be healthy, manifestation of these symptoms is a sign that the shrub is actually ill. These fungi are airborne, sporadic spreaders that attack by entering through any type of wound, including cracks, and through the plant's natural pores. Always keep your pruning tools clean, as unclean tools are a leading cause of disease transfer, explains the Virginia Cooperative Extension. For control, keep your laurel vigorous through proper care, as fungicides are ineffective for this particular disease.