Rose rust

What you see

Bright orange powdery pustules on the leaf underside in spring and summer, with yellow flecking above. In late summer the pustules turn black as the overwintering spores form. Heavy attacks defoliate the bush.

Conditions

Mild, damp weather with long leaf wetness, 18-21C. Overwinters on fallen leaves and on the stems.

Treatment

Strip and bin affected leaves. Sulphur is effective if started early. Do not compost rose leaves.

Prevention

Clear every fallen leaf in autumn and mulch fresh over the bed. Feed with potassium rather than heavy nitrogen. Space and prune for airflow, and choose resistant varieties.

Months: April, May, June, July, August, September

Plants

Rose

Remedies

Wettable sulphur, Potassium bicarbonate spray, Mulch, Wood ash

The thing people get wrong

Rust is far more variety-driven than gardeners accept - two roses in the same bed, same soil, same air, and one will be clean while the other is orange every June. Before committing to spraying a susceptible rose for the next fifteen years, it is worth admitting that replacing it with a resistant variety is less work and more flowers.