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Dahlia with a bad case of Mildew.

NollieNollie Posts: 7,529
in Plants
I was away for a while and my lovely houses sitters watered this as instructed, then the heavens opened...for days on end - poor souls, they were hoping for some sun, which naturally came as soon as they left!

I think it got far too wet, if the mushrooms popping up in the surrounding soil are anything to go by. The mildew is spreading rapidly on the plant.

I am reluctant to lose the flowers by cutting down the affected stems, but am worried it will spread to a nearby rose that is in good health. Is it likely to spread? I would rather protect the rose and lose the Dahlia...

Do I need to wield the secateurs?



Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
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  • ObelixxObelixx Posts: 30,090
    If you can find some, try spraying on an organic fungicide made from horsetail/marestail and see if that fixes it.  They sell it here tho I never saw it in Belgium.

    If not, I'd sacrifice the dahlia to save the rose.

    Vendée - 20kms from Atlantic coast.
    "The price good men (and women) pay for indifference to public affairs is to be ruled by evil men (and women)."
    Plato
  • NollieNollie Posts: 7,529
    No, I have never seen that here, @Obelixx, so you think it may spread to the rose then? It has got it pretty badly...
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • ObelixxObelixx Posts: 30,090
    I just wouldn't risk it.  Dahlias are a lot cheaper to replace than roses.
    Vendée - 20kms from Atlantic coast.
    "The price good men (and women) pay for indifference to public affairs is to be ruled by evil men (and women)."
    Plato
  • NollieNollie Posts: 7,529
    Yes that was what I was thinking, its a trio of my best, healthiest roses and the Dahlia was only a cheapo Lidl one. The secateurs will be wielded pronto. Thanks.
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • SueAtooSueAtoo Posts: 380
    I understand mildew is rather like blackspot, disfiguring but not fatal. Another post suggests garlic water and other remedies - I've used diluted mouthwash successfully on monarda and even my oak tree. Like blackspot remove and burn/discard fallen leaves.
    East Dorset, new (to me) rather neglected garden.
  • PerkiPerki Posts: 2,527
    Isn't powdery mildew caused by being to dry at the roots? And I think for example the rose has powdery mildew its specific to that species of plant it won't affect your dahlia but other roses . 
  • NollieNollie Posts: 7,529
    I appreciate it’s not fatal, but considered the dahlia was probably too far gone to benefit from treatment - the whole plant was covered in it and was looking a bit battered by the rain (I also realised why it had remained so wet, the corner of the guttering above was dripping on it). The mildew may not have spread to the rose but wouldn’t do it much good either in my warm, humid conditions. Anyway, it’s gone now and easily replaced next year!

    Perki, I understood it can be caused by being too wet or too dry???


     
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • PerkiPerki Posts: 2,527
    Sorry for the late reply Nollie , from what I can gather ( maybe someone else can en light us ) Powdery mildew is caused by being to dry and Downy mildew is caused by being to wet . 
  • NollieNollie Posts: 7,529
    No problem Perki. I don’t think I have seen enough mildew to tell the difference, but on that basis it was probably the downy type!
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • PerkiPerki Posts: 2,527
    To confuse you even more Nollie it looks like Powdery Mildew  :D
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