Rose rust

Rose rust is a disease caused by the parasitic fungus Phragmidium tuberculatum and some other closely related species. It is specific to roses, and appears in spring and persists until the leaves fall.

Susceptibility to rust varies widely among rose cultivars, and most modern roses should be resistant to rust.

Rose rust is the least serious of the common rose diseases; black spot and rose powdery mildew are far more prevalent.

You may see the following symptoms:

• On stems: In spring, distorted young green stems, with large pustules of bright orange dusty spores
• On leaves: Yellow spots on the upper surfaces, corresponding to pustules of dusty orange spores on the lower surface. In late summer, the orange pustules turn black. Infected leaves may fall early

Non-chemical control

• Prune out spring infections as soon as they are detected, to prevent the spread of spring spores
• Collect and destroy fallen leaves in autumn to reduce the number of overwintering resting spores
• If infections are persistently troublesome, it may be that the cultivar concerned is unusually susceptible, so consider replacing it with a different one

Chemical control

The fungicides tebuconazole (Bayer Fungus Fighter Concentrate), tebuconazole with trifloxystrobin (Bayer Fungus Fighter Plus), and triticonazole (Scotts Fungus Clear Ultra and Scotts Fungus Clear Ultra Gun) are labelled for the control of rose rust.

The following products contain a combination of both insecticide and fungicide, enabling the control of both insect pests and disease: myclobutanil containing cypermethrin (Bayer MultiRose 2, Doff Rose Shield, Vitax Rosegarde, Westland Rose Rescue); tebuconazole containing deltamethrin (Bayer Multirose Concentrate 2), and triticonazole containing acetamiprid (Scotts Roseclear Ultra and Scotts Roseclear Ultra Gun). When a proprietary product contains an insecticide as well as a fungicide it would be preferable to use an alternative product if pests are not a problem on the plants treated.

Inclusion of a product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.

Download

Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)

Links

Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: storing and disposing safely

The fungus causing rose rust is, like all rusts, a biotroph:  it infects the host tissues for extended periods without killing them, feeding on the living cells. Like all rusts, it is not able to survive on dead plant material, so must either alternate with a different, perennial host, or produce a resting spore to pass the dormant season.

Phragmidium tuberculatum and several other very similar species which infect roses do not have an alternate host; that is, they only attack roses and pass the winter as resting spores.

The first formed spores (spring spores) infect young stems, causing distortion and the production of bright orange pustules. These in turn infect the leaves to produce dusty orange spores (summer spores) which are spread by wind and initiate further infections. In late summer, the pustules producing summer spores switch over to produce the dark, tough resting spores. These spores survive the winter often adhering to stems or trellises.

Infections may be severe enough to cause serious damage, but this is relatively rare and most infections are light enough not to require control.

Disposing of diseased material
Large rose sawfly
Rose
Rose aphids
Rose black spot
Rose dieback
Rose leaf-rolling sawfly
Rose powdery mildew
Rose pruning