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Gardening in the UK

Rust fungus on geraniums - help!

19 years ago

Hi

My geraniums survived through the winter despite being left outside yet the plants all seem to have been affected by the rust fungus. I am getting the telltale signs of red spores on the underside of the leaves and the leaves get circular discolorations on top.

I have been removing the affected leaves, but this seems a lost battle as I have been removing more and more leaves. I have sprayed the plants with fungicide three times now but this does not appear to have had an effect either. Does anyone have any suggestions? The geraniums are still doing okay considering the problems but they could certainly look a lot healthier!

Thanks

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Comments (3)

plantzzman
19 years ago
Sara as Tom Jones would say "Its not unusual!"
I dont actively encourage overwintering plants such as geraniums- partly because I work in horticulture and want to sell more new plants ! but seriously carrying over such plants only leads to carry over of rust etc. I know because it happened to us at work this year when we kept a selection of geraniums to use as living labels for our new sales crop. Talk about a rust explosion !
All you can do is as you have done- remove affected leaves (but try not to strip the plant which needs all the leaves it can get) if possible keep the plants open and not crowded as they dry off quickly after rain etc. Rust loves a damp atmosphere- and its certainly been damp this year as global warmings hot and dry leap frogs us this year. Then get a couple of different treatments from a store for rust- make sure they have different active ingredients and spray as the packaging suggests.
Oh and cross your fingers and hope for drier weather !
shrubs_n_bulbs
19 years ago
Any treatment for rust should be done preventively so that the spores cannot germinate on new leaf and flower buds. Its no good waiting until you have visibly diseased leaves and then trying to cure them, that is not very effective. Those diseased leaves are toast, at best they will hang on in there breeding new rust spores. Rust spores can overwinter on diseased material, although each strain is generally specific to one host plant so your geranium rust probably won't infect your roses. The spores germinate when they are wet (contrast with powdery mildew spores which are killed by water but germinate in warm humid air) and most require to be wet for long periods not just a quick summer shower, so open season this summer :(
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sara_uk
Original Author
19 years ago
Thanks for the info. Unfortunately about half of my leaves are infected now. I had stripped the plants down quite aggressively in places before I sprayed them the first time and, as you say, that has left some parts looking pretty bare. I'll keep trying but it sounds like the geraniums will have to go at the end of the season :(

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