I have grown Fuchsias for many years but I have never seen this before, this is only happening on La Campanella , has anyone else experie
nced this and what causes it ?
That looks like insect damage to me.
Agree with Dove - take a look under the leaves and see if there are any aphids. Greenfly love overwintering on fuchsias kept under glass! Indeed, when I zoom into the photo I can see some dead aphid husks..
Look on the underside of the leaves and you will probably find immature green fly. Rub as many of them off with your fingers (if you are not squeemish) and then spray the whole plant with soapy water (water with a drop or 2 of washing liquid in it). Do this during the day and move the plant into the shade so the sun doesn't burn the leaves (not so likely at this time of year but I am assuming you have them in the greenhouse but thought I should put it in!) You will have to repeat this until they have gone - weekly and you should include all your other plants in the vicinity too. Hope this helps.
Just Googled it and it might be Fuchsia Gall mite,never heard of this before, looks like a dreadful decease.Although it says the leaves will turn a different colour this has not happened so I will treat it as greenfly and isolate the plant just in case.It seems it only affects certain Fuchias,I have 12 different ones but only La campanella is affected.Thanks for your help.
If you want too, you could cut all that damaged growth off, the fuchsia will make lots more strong growth this year.