What Is Wrong With My Sweetbay (Grecian Laurel)?

Are the leaves covered with white powder?

Do the roots and crowns have dark brown spots at the soil level?

Are the leaves discolored?

Are the leaves and twigs covered with small, armored insects?

Are the leaves covered in coarse stippling and may appear silvery?

White, powdery patches on the leaves are caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected plants by thining them and any surrounding plants. Water plants from below to keep foliage dry. Any affected leaves should be cut off and removed. The appropriate fungicidal spray will protect your plant from further infections.

These symptoms indicate fungal disease Phytophthora Root and Crown Rot. Phytophthora pathogens are favored by wet conditions, and the risk of disease can be reduced with good water management. The disease tends to affect plants in poorly drained areas, where susceptible plants are surrounded by standing water or saturated soil for prolonged periods. Provide adequate drainage and know the water needs of individual plants.

Laurel psyllid is an insect that sucks plants sap, causing discoloration and distortion (cupping) of foliage. Adults, about 1/10 inch long, are commonly known as "jumping plant lice", resembling tiny cicadas, covered with whitish waxy filaments. Control them by spraying shrubs in early spring with light horticultural oil to kill adults and eggs. Spray established pests with insecticidal soap every 3 to 5 days for two weeks.

Small, armored insects on leaves and twigs are armored scales. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

These symptoms indicate thrips. Severely infected plant parts should be removed and destroyed. Control thrips by introducing lady beetles or lacewings, their natural predators. Insecticidal soap helps in severe infestations.

Mineral deficiencies can cause tip chlorosis or necrosis or cause foliage to discolor, fade, distort, or become spotted, sometimes in a characteristic pattern that can be recognized to identify the cause. When nutrient deficiencies occur, nitrogen and iron are the most commonly seen deficiencies. Apply only the mineral found to be deficient. Excess nutrients, on the other hand, cause symptoms like leaf tip dieback, marginal leaf chlorosis, necrosis (or burn), branch dieback, and pest problems. In this case, you should provide good drainage, and use good practices during fertilization and irrigation.