Fuchsia rust is a fungal disease that causes orange spots on the undersides of fuchsia leaves and reduces vigour.
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 may be seen all year on indoor fuchsias but in summer and early autumn outdoors.
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 appear on the upper leaf surface, corresponding to orange, dusty pustules on the lower surface. Later, leaves shrivel and vigour is greatly reduced
- 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
Fungicides containing difenoconazole (Westland Plant Rescue Fungus Control), myclobutanil (Bayer Garden Systhane Fungus Fighter and other formulations), tebuconazole (Bayer Garden Multirose Concentrate 2) and triticonazole (Scotts Fungus Clear Ultra) can be used to control rust on fuchsias, but note 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.
The products permitted under organic regimes have little effect on rusts.
The fungus releases orange spores from the pustules and these are spread by the wind to initiate new infections on leaves. In late summer and early autumn these pustules produce dark, overwintering spores, but over-wintering spores are not usually found on fuchsias. These survive over the winter on infected plant material and germinate in the spring to release spores which can only infect Abies, where the fungus goes through a further cycle of development, releasing airborne spores which can reinfect fuchsias. However as mentioned above, the disease is probably present in 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.