Common Rust of Rose
Common Rust of Rose
Rust frequently occurs on rose in the north central states, but extreme winter temperatures limit its severity.
Symptoms: The most characteristic symptom is the appearance of orange cushions (pustules) on either the upper or lower leaf surfaces in late spring and summer. Infected young green shoots may also exhibit long, narrow, orange pustules. The stem lesions may cause twisting of the shoot and destruction of buds.
Cause: This rust is unusual in that it attacks only rose. Spores form on fallen infected leaves in early spring. Spring infections form minute yellow cups of spores on the undersides of rose leaves. The spores become orange in reddish orange cups by summer. These spores repeatedly reinfect the rose. By late fall, the spores are black. These black spores overwinter on fallen leaves and form microscopic, colorless spores that infect leaves in spring. Severe infections defoliate the plants.
Control: Apply a foliar fungicide, as needed, to control the rust. Also, rake leaves in compost or burn them.
