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Downy mildew explosion

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dwhill40

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Hello All,

My little block of vinifera is all but defoliated after a week of steamy weather. I knew I had some downy mildew here and there but dammit. I have been cycling - mancozeb earlier, eagle, and sovran every couple of weeks. I guess maybe this is what fungicide resistance looks like. I began a weekly treatment of captan and agri-phos and I'm seeing new green shoots. I got to verasion and maybe was paying attention to the fruit more than the foilage. Anyone else experience an invasion of downy such as this? Anyone know any clever tricks for eradicating this pestilence?

TIA








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dwhill40

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I forgot to mention, no low brow d-bag comments required. Not all people prefer cat piss flavored wine.
 

KevinL

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I dunno... I found the comment amusing. :)

Jokes aside, I'll take a stab at this since no one else has chimed in. I've only ran into it once myself on a concord bunch. I cut off the diseased material and threw it away. I haven't seen it since. I spray a rotation of Topsin M, Mancozeb, and Myclobutanil. I plan on working Captan in as it is incredibly wet where I am. I've got those fancy disease resistant cat piss vines, so I can't say with certainty if it is my sprays or the grapes that I am growing.

I remember reviewing this when choosing my rotation to make sure my modes of action were different:

http://pested.okstate.edu/pdf/fungicide moa.pdf

It might be worth trying a new mode of action outside of your current rotation and seeing if you get better results. I think there are a few other MOA tables out there that actually have the commercial name of some of the products.

Good luck and I hope your vines recover and pull through!
 

Dennis Griffith

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I've had a marked increase in fungus this year. Had Phomopsis for the first time ever. I blame it the wet cool weather at the start of the season. Up your spray program (like I did), and vary what you are using. Captan, along with Copper is what I'd use this close to harvest. I'd also throw in Serenade, which should help increase resistance to these nasty intruders.
 

wxtrendsguy

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If the ph of your water is low you will want to add hydrated lime with your copper to help prevent leaf burn.

DM across some areas in the east has become resistant to pretty much everything except copper.
 

dwhill40

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Thanks for the replies. My sense of humor died with all of my leaves. Literally a week to defoliate a hundred vines.

Two sprays a week apart using agri-fos and Captan stopped the systemic shutdown. I sprayed copper this morning avoiding the fruit. I now have new growth sprouting so it looks like I saved the vines. The grapes are around 17 brix so I'll let them hang a bit longer and see which way that goes.

I've never used Sovran more than three times a year. It definitely no longer stops DM for me. I'm not sure myclobutanil is working either. I've avoided using copper due reading about the soil accumulation, I've used it only twice the last seven years. Does anyone know if copper accumulation is really a significant issue with occasional use?
 

askins3097

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I had DM on my Niagara vines last year. I sprayed with Captan almost weekly and cut/removed the damaged leaves. I read it stays in the ground and on old foliage, so I made sure I used the leaf blower and cleared the area out in the fall, and also sprayed the ground around the stem. So after all that no DM this year, but I’ve been fighting PM all summer. I’m giving this row one more summer and if it’s a struggle next year, it’s getting ripped out and replaced with a hybrid that’s mildew resistant.

Your troubles are what steers me away from investing in planting vinifera vines living in Pennsylvania. I know it would be a nonstop struggle.
 

Dennis Griffith

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I keep track of what seems to be most effective, and have a ranking system based on what I experience and from what others have reported. So this is my Evidence Based Practices at work. I'll share the spread sheet with you all. It is a dynamic work sheet. Numbers in yellow are fairly firm estimates on effectiveness, but if it just says 'yes', then that is what the product label says. Again, this is for growing grapes here in Southern Ohio. I'll add that Captan is good, but too much use can create a resistance. here ya go..

grapes.jpg
 
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dwhill40

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I had the vineyard immaculately clean to start the year. Sprayed lime/sulpher mix twice in dormancy, My issue started the previous year when a neighbor lined up abt eighty round bails of hay across the road. A couple of vines looked sickly at the end of year so I took extra care to clean up everything. The DM somehow became established. I have another block 1/4 mile away and it has no issues. Spores must be residual in the soil and grass.
 

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