Why Does my Bog Rosemary Look Unhealthy?

Are the leaves covered with white powder?

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

Are the leaves pale on their upper side and are there any dusty blisters on the undersides?

Do the leaves and stems have white, cottony clusters on them?

Are the leaves covered with small bumps?

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 bellow to keep foliage dry. Any affected leaves should be cut off and removed. The appropriate fungicidal spray will protect your plant from further infections.

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

Likely cause for these symptoms is a fungal disease - Rust. Provide good air circulation around plants by thining them. Avoid making leaves wet when watering. All infected leaves should be removed. Spray leaves with sulfur early in the season to prevent rust or to treat mild infections.

White, cottony clusters on leaves and stems are caused by mealybugs. These tiny insects are covered with a fluffy white coating. They feed by sucking plants sap. They produce sticky substance honeydew which makes leaves sticky. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Leaves covered by small bumps are caused by 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.

Bog rosemary plants have specific environmental requirements. They must have moist, acidic soil, cool summers, and good sun. Under these conditions, they thrive. If their needs in any one of these respects are not met, they will not do well.