What is fuchsia rust?

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).

Symptoms

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

Control

Non-chemical control

• Fuchsia enthusiasts should avoid ornamental species of Epilobium and eliminate weedy species
• Pick off affected leaves as soon as they are noticed and feed the plants to boost vigour

Chemical control

The fungicides tebuconazole (Provanto Fungus Fighter Concentrate), tebuconazole with trifloxystrobin (Provanto Fungus Fighter Plus, Toprose Fungus Control & Protect), and triticonazole (Scotts Fungus Clear Ultra and Scotts Fungus Clear Ultra Gun) are approved for the control of rust diseases on ornamental plants, and can be used to control the disease on fuchsias. However, tebuconazole and triticonazole both 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.

We suggest spraying a few leaves first and waiting 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.

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

Links

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

Biology

The fungus releases orange spores from the 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.