Gewurztraminer (V.Small Scale) - Problems (Mildew?)

[glypo]

Hello all, I'm new here. I joined so that I could read through old posts to help identify an issue I'm having.

I live in the south of England (Surrey) and for three years I have been growing Gewürztraminer - in pots - on a very small scale indeed. I have just four vines. I am in my early thirties and have no experience of grape growing prior to this. My intention is to scale this up to approximately thirty vines over the coming year or two, once I have property with sufficient space. I have been consulting a handbook: "Grapes: Indoors & Out" by Harry Baker and Ray Waite of the Royal Horticultural Society for the past years and this has been very handy.

I am training the vines to a standard and this year is the first year that I have allowed fruit to grow. In the last days something rather extreme has happened and the vines are rapidly dying. The leaves are falling off, all growth has stopped or slowed, even new leaves are growing brown in colour. I cannot track the cause or solution to this problem, and fear my vines will be dead in days. I have read through the chapters on mildew on the aforementioned handbook - when searching for images online I have failed to establish whether this might either downy or powdery mildew. To me it looks quite different to the examples I have found online. I am hoping that someone here, who would undoubtedly be more expert in the matter, would be so kind as to confirm from these images as to whether this is powdery mildew (or something else). If so - is it terminal and the end of my vines?

Thank you very much indeed for your help, stay safe!

Example of new growth:

A fallen leaf:

Perhaps sun scorch mixed with mould?

The worst of the four:

The best of them:

One final example:

 

[user 36973]

Looks like downy mildew. The telltale sign is that the yellow on the front of the leaf is paired with grey on the back of the leaf.

 

[glypo]

Thank you so much, it is very greatly appreciated. At least now I have some confidence in the problem, so that I can try to solve it. I've just been reading some old threads on this site about downy mildew so have a variety of ideas now.

I will try something more hardy to disease, perhaps Phoenix or Orion, if I fail to save these.

Thank you once again.

 

[user 36973]

Are your vines on their own roots or grafted? Unless they are grafted, they are susceptible to phyloxera. I had some non-grafted cab franc that died after a few years due to phyloxera. Having them in pots may help, but I've not seen grapes grown in pots before.

 

[user 36973]

I've just been reading some old threads on this site about downy mildew so have a variety of ideas now.

Captan is a widely available pesticide effective for downy mildew. You can find that in many fruit tree sprays at a garden center

 

[glypo]

Thank you very much for your continued help, you have an encyclopaedic knowledge! My vines aren't grafted, they have their own roots. I don't believe phyloxera is a major problem in England right now (based on this link) and hopefully the pots will mitigate this a little too (I can at least hope). Potted vines are fairly common in the UK for amateurs - especially because of our climate and the need for many varieties to be moved under glass in later summer and autumn in order to ripen the fruit. The typical sparkling wine grapes are amongst the few that succeed in proper vineyards here. I had a look at Captan - unfortunately it seems there isn't a fungicide to tackle downy mildew available to amateurs in the UK, they appear to be banned and/or limited to commercial (regulated) growers. I popped to my local garden centre at your suggestion and found a few funcide sprays for use against power mildew and others (I bought one spray to at least try) and have ordered an organic spray as described in the RHS link - which hopefully arrives in time.

Once again, thank you! Your help is invaluable.

 

[user 36973]

Best of luck. I'm also growing Seyval blanc (widely grown in the UK) and can confirm that it is vigorous and own rooted. It is slightly susceptible to downy mildew and black rot. This may also be a good option.

Cheers.

 

[Dennis Griffith]

IMO. your problems doesn't start with the fungus, but the pots. First, your pots look to be too small. Grapes like room for their roots. If I was going to grow in pots, I get some large muck buckets (used in cleaning horse stalls), and drill some holes in the bottom for drainage. I have been growing sweet potatoes in these and the buckets are full of potatoes by the end of the season. Second. grape vines will pull most of the nutrients out of the soil in a pot after a couple of years, so your vines are probably stressed from this lack of nutrients, which brings us around to the fungus. Stressed vines are more susceptible to disease. If it were me, I'd have the leaves/petioles tested to see what the vine was lacking. And you can treat the vines with Captan for the existing problem. There are also biological treatments like Serenade or Actinovate that can be used. Think like a greenhouse grower; they don't like a lot of chemicals on their plants as it can accumulate in their closed environment. Pots are an enclosed environment.

 

[Xnke]

Dennis is correct. If your pot cannot hold 1m^3 of soil, it is not large enough for a grape to grow in. On my rooted cuttings, I start with a 3L container, then a 12L once growing, and either into the ground or into a 1m^3 container.

 

[glypo]

Dear Dennis and Xnke, thank you very much indeed for your help. Perhaps the photo is at a misleading angle to properly display the size of the container – of one thing I am certain is that the vines are in appropriately sized pots. At least I was certain . The Royal Horticultural Society recommends a 13-18 cm (5-7”) pot for the first and second year, before potting into a final container in year three, this will be the container for the life of the vine. These are most commonly half barrels (circa 90 litres) and there are many hundreds of examples of these locally, vines decades old in circa 90 litre containers - this is what inspired me. The containers I have are 45 centimetre cubes, which is around 90 litres, and were deliberately chosen as such. They are potted with a loam-based compost (stops the vine becoming top heavy) and full of nutrients. As my vines are three years old this year I repotted this spring, they were all thriving until a few days ago. By my calculations a cubic metre container would be impractical - 1,000 litres of soil and about 740 kg of loam based compost. The intention of containerised vines is to give flexibility in the English climate, moving the vines out of the greenhouse in summer to ripen the fruit. As above, such a large size isn't required - I spoke to the experts at Wisely before embarking to ensure that was the case.

Being new soil (John Innes No.3) there is plenty of nutrients, I feed them a high potash feed weekly, and intend to scrape the top annually. I am literally following the book in this regard, so believe these nutrients aren't my issues - though I am very grateful for the helpful suggestions.

Regarding Captan - as above unfortunately this isn't legal for home gardeners in the UK - in fact no fungicide that tackles downy mildew is available to me. Consequently, based on jgmillr1's advice above I've been exploring organic treatments. I will keep my fingers crossed. Once again, thank you very much for your kind input.