Fuchsia rust is caused by the fungus Pucciniastrum epilobii. At first, the disease typically causes leaf spots and/or patches which first appear pale or discolored; they may then turn tan,
occasionally with a purple-colored border. Spots are followed by the colorful yellow-orange sporulation of the fungus on the under and/or upper leaf surfaces. In severe cases, leaf drop may occur. In the samples seen this spring, leaf spots were not particularly conspicuous, though lots of sporulation was observed.
While problematic and unsightly for your fuchsias, you don't need to worry about this fungus spreading to other annuals in the greenhouse—rusts are very host specific. P. epilobii infects fuchsia and fireweed (Epilobium), with true fir (Abies) as an alternate host.
If you see fuchsia rust, carefully discard plants and leaves to avoid spreading spores (bag them before carrying through the greenhouse). Follow with fungicides to protect healthy fuchsia from infection. A number of fungicides are labeled for rust, so make sure to rotate between modes of action or fungicide groups. Using a systemic fungicide is a good place to start, then rotate with a different fungicide group.
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