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Grapevine concern!!

MuscratMuscrat Posts: 7
in Problem solving
I have cultivated a grapevine in my greenhouse which is now in it's 3rd year and has been strong and healthy however over the last couple of weeks I've become concerned about a discoloration in its leaves, lateral stems and tendrils. I'm fairly sure it's a type of mildew but what type? What would be the worst case scenario if left unmanaged and what would be the best course of action to stop the disease. I have attached some photographic evidence to aid recognition, if anyone has any advice I would be greatly appreciated, I've spent a lot of time and effort getting it this far and would hate to loose it.

Posts

  • AmphibiosAmphibios Posts: 158
    Hi @Muscrat hopefully someone who is knowledgable on Grapevines will be on soon who may be able to help you out. 
    Otherwise it might be an idea to post on: 
    https://www.reddit.com/r/viticulture/
    It’s a relatively small subreddit but  super knowledgeable. Reddit tends to have more of American users but I’m sure they’ll be able to help you. 
    Hope you get the help you need! 

    A x 
  • PerkiPerki Posts: 2,527
    I can't say I've seen this before , is it tacky to touch ? And have you got some pictures of the leaves and the whole plant. what sort of watering have you been doing ? I can't see it being Botrytis ( grey mold ) at this time of year its a lot more common in autumn , but its a possibility is the vine outside or inside , getting botrytis outside in this weather is extremely unlikely . 
  • Blue OnionBlue Onion Posts: 2,995
    Is it sticky?  Do you have a tree above or near to the vine?  Looks a bit like honeydew drops.
    Utah, USA.
  • MuscratMuscrat Posts: 7

    Hi, here are a few more photos.
    The vine is in a greenhouse, I generally water it twice a week usually between 1 and 2 gallons each time depending on the greenhouse temp and feed with high potash fert every fortnight. The stem patches are not sticky. Cheers
  • Blue OnionBlue Onion Posts: 2,995
    Downy mildew?
    Utah, USA.
  • DovefromaboveDovefromabove Posts: 88,147
    edited June 2020
    How much ventilation is it getting?  That looks mould/fungal you mr ... I would think it would need the maximum ventilation possible in the recent hot weather ... and probably shading too, to protect the tender young leaves. 

    Mature vine leaves are able to cope with strong sunlight but, on my outdoor vine at least, the leaves were still
    unfurling during the scorching weather ... I think that even on an indoor vine the leaves would’ve been very young and tender and probably would’ve scorched in the strong sunshine. 

    Take a look here ... there’s a section on Mildew https://www.chrisbowers.co.uk/article/ultimate-guide-growing-grapes/

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.





  • FairygirlFairygirl Posts: 55,117
    I'd agree. The kind of heat recently would mean anything in a greenhouse without adequate ventilation and some shading will struggle, especially with new, vulnerable foliage. 
    1 or 2 gallons of water twice a week doesn't sound very much either.
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • DovefromaboveDovefromabove Posts: 88,147
    I agree re the water too @Fairygirl ... for the past two weeks I’ve been leaving the hose running at the base of my outside vine  for half an hour twice a week. 

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.





  • FairygirlFairygirl Posts: 55,117
    It'll be evaporating very rapidly in a hot greenhouse too, I'd have thought.
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • MuscratMuscrat Posts: 7
    Hi all, thanks for all your very valid comments, as I'm not an experienced grape grower each season's new growth has possed new challenges, this season has been coping with the unexpected dense growth of the conopy and how to keep it healthy, even though my greenhouse is extremely well ventilated the temperatures lately have been excessive as you've rightly mentioned and with very little breeze the air in the greenhouse has been stagnant and I fear this and the overcrowded growth and lack of shading has contributed to right conditions for the onset of this vital attack, now my issue is how to stop it's advance..... Any thought on remedies would be most appreciated.

    Thanks all.
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