Grapevine disease identification

[JT101]

Hi all




Might have one or more diseases. Setup my mini vineyard on my allotment in south East London. Mostly seyval blanc and regent, not on rootstock. Grown from cuttings.




As you can see from the photos, many have that classic bumpy surface, with a somewhat yellowy powder on the back. And many leaves have curled up and turned brown: here is a video of them: https://youtu.be/rFs-OGngc4I




Definitely affecting the vine. I have one other vine on the plot (may be a dofferent variety since i did initially have several) which seems to be unaffected, and has plenty of bunches of grapes, so I would expect the affected ones to have similar growth, but any bunches seem to have withered.

thanks in advance

[JT101]

Some more pics

[ameno]

Grape blister mite is causing the bumps, and causing that stuff on the underside of that leaf (it's not fungus, but an overgrowth of hairs). Blister mite is not harmful to the health of the vine, so can be ignored.

I notice that the brown patches are red on the inner edge, and some of the leaves have red patches around the outside of the leaf, even though they're not browning yet.
That being the case, I strongly suspect nutrient deficiency. Lack of potassium, magnesium and phosphorus can all cause reddening in red grape varieties, and considering you say fruit are withering, too, it may be potassium. However, considering the weather I suspect the indirect cause is not a soil shortage of these minerals, but rather simply a lack of water, which makes it harder for the plant to take them up.
Try giving the vines with red leaves a good soak, and again a week or so later if it doesn't rain, and see if they perk up.

[JT101]

THanks ameno. I've done what you said, plus there has been plenty of rain so they are well watered. Can the deficiency of these elements causing the deformities I see in thsee leaves, not just discolouration? That's what made me think it was a disease.

cheers

[ameno]

The bumps and the white fluff are caused by grape blister mite, as I said. They're fairly harmless.
I'm not sure I see any other deformities?

[JT101]

Having looked at a bunch of diseases online, I'm a bit worried this is Pierce's disease..........

[ameno]

Having looked at a bunch of diseases online, I'm a bit worried this is Pierce's disease..........

That's caused by a bacterium not known to have arrived in the UK yet, so you'd have to be extraordinarily unlucky for your grape vine to be patient zero.

[JT101]

I agree, the bumps are grape blister mite, but it's the scorched leaves i'm worried about. Doesn't seem to resemble a deficiency in any mineral (from what I can tell by looking at pictures online). They look most similar to Pierce''s disease (which as you point out is probably not here yet) or maybe angular leaf curl. It doesn't look like much else. But i'm only looking online.

as a hobbyist grower I don't have access to grapevine experts to visit my site or lab tests and verify what it is. What can I do to A) identify the problem, and B) to get rid of it.