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Diseases of Geraniums

geranium image by szildy from

Geraniums are a popular flowering annual that can be used in flower beds and flowerpots and baskets. There are hundred of varieties, and blooms are available in many colors. Because of the sheer number of geranium cultivars, most everyone can find one that is suitable for their conditions and climate. Geraniums are considered easy to grow, but they are susceptible to some diseases.


Geraniums are susceptible to multiple types of leaf blight, including Botrytis blight and bacterial blight. In both cases, plants with blight will have discoloration or damage on the leaves of the plant. With Botrytis blight, the leaves can develop patches of gray fungus or large locations with dead foliage. It usually develops in areas with high heat and humidity. Bacterial blight can cause brown, V-shaped spots on the leaves or darkened veins. You can prevent blight by carefully maintaining the plants and keeping the bed free of weeds and plant debris.

Root Rot

Root rot can cause the stems of geranium plants to wilt and turn yellow. It is a fungal disease that develops in hot, humid areas. Some geraniums with root rot may develop black spots near the soil line, and the roots will appear decayed and damaged. The best way to protect against root rot is to plant in a well-draining soil and avoid overwatering.

Leaf Rust

Leaf rust is a fungal disease that affects geraniums and other plants and flowers. Geraniums with leaf rot can develop pustules that look like rust. These pustules can break open and cause a circular, rust-colored mark on the leave. In addition, yellow spots may develop on the leaf tops. Leaf rust can be avoided by properly planting and maintaining your geraniums and removing dead and diseased plants. If your flowers develop leaf rust, you can apply a fungicide to treat and control it.

Leaf Spots

Two types of leaf spots can develop in geranium plants: Cercospora and Alternaria. Cercospora leaf spots are small, sunken gray spots, while Alternaria leaf spots are similar in appearance to blisters and typically develop on the underside of the leaves To avoid leaf spots, water your geraniums in the morning and be sure the plants are not overwatered or allowed to sit in water. Also, remove leaves affected by leaf spots to prevent it from spreading.

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