New Vines Stopped Growing - Powdery Mildew?

[johngg123]

Many of my Pinot Noir and Zinfandel have stopped growing. They appear to have been "frozen" in time. Some are even "stuck" at bud break .. like a popcorn kernel just popped but then no shoot. Does this look like powdery mildew? What can I do to control it and bring them back to life?

Seems to just affect the Pinot and Zin. My cabernet sav is taking off, almost already at the wire!

Thanks,
johngg123

 

[grapeman]

Yes you have a bad case of mildew. Those varieties would be more susceptible to it. If you had grow tubes on them, that would be the problem. If not, then it is staying too wet for them. You would benefit from a fungicide of some type- I won't say which ones because you have different one approved where you live. Ask at a garden center and they can point you to some. Check the label to see if it is effective for grapes especially downy mildew or powdery mildew. Keep air movement free to them. If you can get it under control, they should grow new shoots where they die back. Not a good start.

 

[johngg123]

Grapeman, thank you! Yes, they have grow tubes... I removed the grow tubes and we are having very hot and dry weather today, hopefully that will help. (80 degrees, 20% humidity.) I'm looking at using Spectracide Immunox (Myclobutanil) for a systemic and then using Captan for downy mildew protection. Also considering Mancozeb instead of Captan. Any thoughts?

All are okay for grapes, according to:
http://www.caes.uga.edu/extension/habersham/anr/documents/Fungicide.pdf

 

[grapeman]

Mancozeb is for early season control once they begin to bear. Captan will work all season. Opening them up along with warm dry weather should put a stop to it.

 

[johngg123]

Okay, cool. I'll keep an eye on them and hold off on the spraying for now! (fingers-crossed)

 

[johngg123]

After further research I think an eradicant is needed because the fungus is established. Seems that powdery mildew it is quite a problem in here in California even with our hot dry weather.

"...no moisture is needed for the fungus to establish itself and grow after infecting the plant. Powdery mildews normally do well in warm, Mediterranean-type climates. Thus powdery mildews are more prevalent than many other diseases in California’s dry summer and fall seasons." [1]

I decided to give Neem Oil a try because it is classified as an eradicant of powdery mildew[1] and I have it in my garage . While probably too expensive of a solution for a large vineyard, Neem Oil is well priced for my handful of vines. Hopefully it works!

Reference:
[1] http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7494.html

 

[grapeman]

John I am from the east and not sure if downy mildew is a problem where you are, but that looks somewhat like downy mildew, not powdery. PM has a dusting appearrance like the link you show where downy mildew is more of a fuzzy appearance like in your pictures. But then again usually the fruiting bodies of the fungus are on the unerside in DM. Either way they require two different sprays. There have been studies here at Cornell that show that sunlight is enough to kill PM during sunny, dry periods. I guess what I am trying to say is that while it could be one or the other, treatments are different and usually you need to use both spray programs.

 

[johngg123]

Grapeman, great point. I would describe the leaves as both fuzzy and dusty so I'm not much help there! DM is definitely possible in California since we had some warm spring rains and I was using grow tubes.

I have Bonide Liquid Copper Fungicide (Copper Soap) which advertises as being effective against DM for grapes, but can it be used with neem oil? I'm about to order a bottle of Captan does that have any issues with being used alongside oil?

DM link:
http://www.ipm.ucdavis.edu/PMG/r302101111.html

 

[grapeman]

You can't use Captan and oil together safely. It is worse in warm weather and can burn the leaves. You might be able to alternate their use- check that out.

 

[blumentopferde]

That looks very much like powdery mildew to me. Downy mildew would create lots of yellow and brown stains on the leaves, small shoots would dry and die before they unfold.

I've heard that milk or whey solved in water in a concentration of about 10% might help, you might also try to wash it off with lots of soapy water!

 

[johngg123]

I think the neem oil is working against the mildew (along with hot weather and removal of grow tubes!)

However I have a couple vines that have a leaf near the bottom that is faded with brown spots. Is it a bad thing? Disease? Hope I'm not being paranoid. I just pluck them off. (See photo)

Another issue may be that my yard is infested with household black ants. Some of the vines are now in what has become ant hills. I've started efforts to control them in anticipation of fruit in a few years. Can they hurt the roots or stunt growth in young vines? They are just in the dirt, not on the vines.

John

 

[johngg123]

Things are now going well. A couple of vines (out of 30) continue to have some yellowing leaves. Here are some new pictures. It seems to just be on the lower oldest leaves. Any ideas?

I fertilized with half strength miracle grow two weeks ago. They've been getting plenty of water (twice a week.) Been spraying with neem oil every 1-2 weeks.

 

[johngg123]

upon further research I'm narrowing this down to either:

1.) Nutrient Deficiencies
or
2.) Overwatering

I'm watering twice a week in heavy clay soil. Maybe that is too much. The soil test showed very low Nitrogen. I've only used half strength Miracle Grow once.

At this point I think I'm going to dial back the watering and apply more fertilizer.

Thoughts?

 

[johngg123]

More images. These are the same leaves as above. They continue to change colors! Help!

 

[GEM]

John,

Is your soil clay? I do think you are watering too much for your soil, so going to once a week might help. If they look like the leaves are drooping, give them some water, otherwise, once a week. Also, your PM may come back so you need to keep on it if you see any signs of its return. There is usually an explosion of PM once it is seen, so hit it soon as you see any sign of it. Look at UC Davis Pest Management for grapes. Drop me an e-mail if you need more info on that link. Cheers, Gary

 

[blumentopferde]

Check the downside of the leaves whether there is a white powdery film on it. If yes, it could be powdery mildew!