What is Geranium Rust?
Geranium rust is a disease caused by the fungus Puccinia Pelargonii-zonalis. It originated in South Africa, but over the course of the 20th century, it spread throughout the world, reaching the continental United States in 1967. It is now a serious problem for geraniums worldwide, particularly in greenhouses where quarters are close and humidity is high.
Geranium Leaf Rust Symptoms
Rust on a geranium begins as small, pale yellow circles on the underside of the leaves. These spots quickly grow in size and darken to brown or “rusty” colored spores. Rings of pustules will surround these spots, and pale yellow circles will appear opposite them on the upper sides of the leaves. Heavily infected leaves will drop. Untreated geraniums with leaf rust will eventually become completely defoliated.
Treating Geranium Leaf Rust
The best method of geranium leaf rust treatment is prevention. Only buy plants from reputable sources, and thoroughly inspect leaves before purchasing. Spores thrive in cool, damp conditions, and are especially prevalent in greenhouses. Keep your plants warm, space them well for good airflow, and keep water from splashing on leaves during irrigation. If you see signs of rust, immediately remove and destroy infected leaves, and treat the rest of the leaves with fungicide. If a plant is heavily infected, it may have to be destroyed.
