What's wrong with my grapevine?

[jonty59]

For the last 2 years my (10 yr old) grape vine has developed a disease which I believe to be powdery mildew. Last year I sprayed early with Bayer Fungus Fighter a few times but no improvement. This year I've been spraying very 2 weeks but it's looking even worse than usual at this time. Any thing I can do apart from ripping it out?

The photo is typical of the entire plant. Brown patches on leaf edges, white bloom on new leaves, curling leaves, deformed shape, leaf colour dull green etc.

Any ideas what is wrong and maybe how to cure it?

[Kirk]

Where is the vine? Last time I had one after 10 years it was bigger then the images would imply of yours.
Stress seems a likely cause as it simply weakens the plant and so makes attack easier.

Cannot be sure about options to use as the RHS site says there are none available to amateur gardeners, then gives a pdf of fungicides for gardeners which has a date of March 2017, so recent. And there are ones in there for mildew.

Last year was odd and this year has also been odd, we had about 1mm of rain in all of April and drought stress is mentioned by the RHS. So 2 odd years and you mention 2 years of mildew.

Can only think of somehow supplying it with a less stressful environment. You could I suppose find that what we consider stress free is not what a plant does, they tend to just grow whereever and get on with it.

Have a look at the RHS site: https://www.rhs.org.uk/advice/profile?PID=569
Maybe alter something. As usually a virus/fungus attack is caused by a weak plant, a strong one fights it off fairly easy.

[fishpond]

H Jonty59
Whereabouts in the world are you based?

[Zelenina]

I can't see any mildew there. Maybe a nutrient problem. What is it growing in? Do you feed it with anything?

[Deltawhiskey]

Hi Jonty59,
Firstly, what variety is the vine and has it grown well in the past and born fruit. The new leaves on a vine are often 'furry' which can look like mildew. It looks to me more like water stress. In ten years the roots should be deep enough not to be troubled by lack of water but only if they can get deep enough. The vine is planted next to a wall and may be affected by the foundations blocking the roots. Watering may help and mulching will keep the soil moist. The browning could also be caused by a lack of nutrients. Mulching with a good compost could help if this is the case. There is a wrongly held belief that vines don't need good soil to grow. This is wrong, which is why most vineyards continuously improve their soil. You can also try foliar feeding with Maxicrop. This will feed the vine and with the trace elements in it strengthen the growth against attack.

Hope this helps

David

[jonty59]

Grapevine replies

Thanks to Kirk, Fishpond, Zelenina and Deltawhiskey for your thoughtful replies.

Background info - location Cotswolds SW England. It's an ornamental vine but don't know specific variety. I bought the house 3 years ago, neighbour reckons vine could be 10 yrs old. It grew vigorously first 2 years but got mildew both years and fruit shriveled and lost leaves in early August.

The soil by the house is not great so I added compost mixed with some miracle grow to the soil at base of plant in mid-May but no visible change.

Most everyone thinks it's not fungal - which is good I guess.

I've attached some more photos incase anyone has any more ideas


Thanks again to all for your support so far

[jonty59]

Photos

[Deltawhiskey]

Hi Jonny,

I am glad you sent the new pictures especially the one showing the ground. The vine is planted on top of the house foundation and it looks like there is also another wall across from the house wall which will stop the roots going that way. On the other side there is what looks like a step stopping the roots going that way too. If the roots are blocked by the foundations then water stress would seem to be the problem. Try really soaking the soil around the base of the vine once a week. If the vine improves you have the answer.

David

[Deltawhiskey]

I have also just noticed that there is paving paving over the top of the area where the roots would be. This would prevent water penetrating the soil because it is probably sloping to take the water away from the building.

David

[jonty59]

grapevine reply

David - thanks for your reply and sorry for delay. I've been watering regularly without improvement. Do you think it could be russet mites? There are lots of 'furry' white spiders web type growths on the leaves. I'm thinking to try Neem oil. What do you think?
Jonty59

[Deltawhiskey]

Hi Jonny,
The leaves are quite deformed, curved instead of flat and could be the result of red spider attack. Check under the leaves for little red dots. A systemic insecticide should get rid of the little blighters.
David

[Jungle Jane]

If you've got furry,white spiders web type growths they could be from a little caterpillar if it's what on the leaf in one of the photos,spider mite webbing looks different,check leaf edges,you'd see an infestation. Have you ever pruned the vine? It's important to cut it back a bit once a year,if you already do this then maybe a hard pruning would give it more chance but I don't know about pruning it now it could bleed sap,although I do cut the odd bit off mine & it never does. I wouldn't use any insecticide we don't know what the problem is yet?

[jonty59]

Answer to grape vine problem

Thanks to everyone who helped me on this thread. The cause of the problem turns out to be spider mites - see photographic evidence





The underside of leaves are covered in webs and you can see the mites clearly under a microscope. Photos were taken 10 days after liberally applying Neem Oil solution twice in a week. That doesn't seem to have worked so will go for Bug Clear Ultra (acetamiprid) to try and get rid of them finally.

(Note - I prune the vine back every year so it is well under control - but it does seem susceptible to disease - It's had powdery mildew, scale insect, and now mites)

Do come back with any comments.

Thanks again!

[Deltawhiskey]

Hi Jonty,
I am sorry to hear about all the problems with the vine. Perhaps that is why it hasn't grown as large as it should. One thing you could try is spraying regularly with Maxicrop. It will foliar feed and add trace elements. Spider mites do not like the damp spraying under the leaves will cause. The other benefit is that Maxicrop will toughen the leaves making the less susceptible to attack. At the end of the day you might consider replacing the vine with one of the hybrids which are resistant to mildews. I planted in April and had to pinch back mid June when the vines reached 8 feet. Planting a good vine will pay dividends and provide you with some grapes. You do not know the variety you have, which may be one of the older disease prone ones that need regular fungicide spraying.
David