Why Does My Black-Eyed Susan Look Sickly?

Are the leaves covered with white powder?

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

Are the leaves curled and distorted?

Are the flowers deformed or dwarfed?

Do the leaves have small holes?

Are the leaves spotted or blotched?

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. Any commercial fungicidal spray will protect your plant from further infections.

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.

Distorted and curled leaves are caused by aphids. These tiny insects cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted and later leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Tarnished plant bugs inject a plant-deforming toxin as they feed on young leaves. Trap them with white sticky traps or treat plants with a commercial pyrethrin spray or dust in the evening to control severe infestations. The best way to prevent this pest is through a thorough fall and spring cleanup. This will prevent it from overwintering.

Small holes in Black-Eyed Susan's leaves are caused by sawflies. Sawfly adults are small black and yellow wasplike insects with 4 wings. The larvae are 1/2 inch long, dark olive-green with white spots, and resemble caterpillars. These larvae feed on violet leaves at night. They chew holes in lower leaves and may defoliate entire plants. Spray the pests with methoxychlor or malathion.

Your plants might be suffering from fungal leaf spots. 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.

If the stems of your plant rot at the base, most likely cause is a fungal disease - Crown rot. Leaves and stems turn brown at the base, the foliage turns yellow and black spores may appear on the stems. Remove and discard any infected plants and their surrounding soil in the trash to limit the spread of the disease. Keep winter mulch away from the crowns to reduce problems.