To prevent all the diseases mentioned below, here are the four golden rules to follow:
1°) No watering late in the evening, nor in full sun
2°) Water without overdosing: it is better for the soil to be too dry than too wet.
3°) A balanced supply of fertiliser without overdosing.
4°) A well aerated soil for fuchsias in pots.
Here is a list of the diseases most often encountered on fuchsia:
Puccinia epilobeii (brown rust): Manifested by a small halo on the upper surface of the leaves. And on the underside a round brown dusty spot.
Fumaginia: Fungus that develops on the aphid meillium. It is sufficient to control the aphids.
Botrytis cinerea: Fungus that develops in wet winter conditions and by repeated rain and average temperatures below 15 degrees.
Root rot: Caused by overwatering and poorly draining soil or potting mix.