Rose Plants & Rust Fungus

Identification

• Rust fungus is bright reddish-brown to bright orange in color. It's a powdery substance that forms in spots and looks somewhat like warts on the rose plant.

Location

• Rust fungus spores begin to attack rose plants on the underside of leaves and on stems. However, if you do not treat the fungus quickly, it can spread to the top portion of the leaves and possibly even cover the plant.

Effects

• Left untreated, the rust fungus on rose plants will turn dark brown and even black. The fungus will kill the leaves of the plant, causing them to wilt and fall off.

Season

• Rust fungus can grow only when the temperature is below 85 degrees F, typically in the spring season or a wet climate.

Geography

• Rust fungus on rose plants occurs most in the Pacific Coast region. Areas of the U.S. that have hot summers and cold winters do not often see this condition.

Treatment

• Cut off affected areas immediately and dispose of them in the garbage (do not compost them). Prune the plant in early spring before new buds bloom and apply sulfur and lime sulfur or an oxycarboxin chemical to keep it under control. Avoid over-fertilization of the plant.