Fuchsia rust is a disease caused by a fungus, Pucciniastrum epilobii, that spreads by airborne spores and reduces plant vigour. Rust is found in summer and early autumn on outdoor plants, but may be seen year-round on indoor fuchsias.

The fungus infects willowherbs (Epilobium spp.) as well as fuchsias and alternates between these hosts and Abies spp. (firs).

You may see the following symptoms:

• On leaves: Initially, pale, ill-defined yellow spots or blotches appear on the upper leaf surface, corresponding to orange, dusty pustules on the lower surface. The affected areas of the upper surface may turn a purple colour on some cultivars. Later, leaves shrivel and fall, and vigour is greatly reduced

The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.

Non-chemical control

• Fuchsia enthusiasts should avoid ornamental species of Epilobium and eliminate weedy species
• Avoid wetting the leaf surfaces if possible, particularly of plants already affected by the disease
• Pick off affected leaves as soon as they are noticed and feed the plants to boost vigour

Fungicides

The RHS recommends that you don't use fungicides. Fungicides (including organic types) may reduce biodiversity, impact soil health and have wider adverse environmental effects. If you do intend to use a fungicide, please read the information given in the link and download below to ensure that use, storage and disposal of the product is done in a responsible and legally compliant manner.
  
The products listed in the ‘Fungicides for gardeners’ document below are legally available for use by home gardeners in the UK. This information is provided to avoid misuse of legal products and the use of unauthorised and untested products, which potentially has more serious consequences for the environment and wildlife than when products are used legally. Homemade products are not recommended as they are unregulated and usually untested.

Tebuconazole and triticonazole, two fungicide active ingredients contained in products carrying label recommendations for rust control on ornamental plants, belong to the triazole group of fungicides. It should be noted that fuchsias are stated to be very sensitive to damage by this type of fungicide and some authorities say that they should not be sprayed. Alternatively, spray a few leaves first and wait at least three weeks to see if any damage occurs. This wait may mean it is then too late to spray in that season, but will give an indication of whether spraying can be carried out safely in future years.

Download

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

Link

Chemicals: storing and disposing safely

The fungus releases spores from the orange pustules and these are spread by the wind to initiate new infections on leaves during wet conditions. Part of the life-cycle of the fungus is spent on Abies species, and spores produced on Abies are able to infect fuchsias (and Epilobium species) in the vicinity. Spread of the disease onto fuchsias from infected Epilobium is also possible. However as mentioned above, the disease is probably present on fuchsias all year anyway.

The rust fungi are described as biotrophs: they grow within the living tissues of the plant and extract nutrients from the cells over an extended period. However, although they do not kill tissues rapidly, heavy attacks by rusts can cause tissues to collapse and die prematurely and this is the case for fuchsia leaves. This leads to a great loss of vigour and an unsightly plant.