Leaf disease trouble

[lmshelly]

So I've got 27 vines of marquette but every year without fail the leaves seem to become diseased despite maintaining a strict fungicide (mancozeb) spray schedule. I'm not sure what the culprit is... pictures posted below in case anyone has any insight.

I used to have a section of traminette but the disease got so bad the vines weren't viable so I had to pull them. Unfortunately I have no agricultural expertise...

 

[ChuckD]

Are the grapes diseased? Does it seem to impact vine productivity or hardiness?

 

[lmshelly]

Are the grapes diseased? Does it seem to impact vine productivity or hardiness?

Neither from what I can tell. My profile picture is of a current cluster. Vines are 4 years old and haven't noticed any issues with the vine development that I can tell.

 

[wood1954]

Mancozeb does nothing for powdery mildew. Sulfur, tebuconazole, or myclobutanil will help for powdery mildew. Also mancozeb has a phi of 66 days so I stop using it around July 4. You need to protect your vines until the first frost.

 

[lmshelly]

Mancozeb does nothing for powdery mildew. Sulfur, tebuconazole, or myclobutanil will help for powdery mildew. Also mancozeb has a phi of 66 days so I stop using it around July 4. You need to protect your vines until the first frost.

The "rust" look in the pictures above doesn't seem like powdery mildew... although I will definitely take that advice and add something to the regimen to prevent it from occurring in the future. I just read on here a bit ago that Marquette might be sensitive to sulfur? Maybe best to use one of the others you suggested?

And does your last sentence mean I should be spraying after harvest until first frost? I'm fairly new to this so that would be helpful information!

Thank you!

 

[Cynewulf]

The "rust" look in the pictures above doesn't seem like powdery mildew... although I will definitely take that advice and add something to the regimen to prevent it from occurring in the future. I just read on here a bit ago that Marquette might be sensitive to sulfur? Maybe best to use one of the others you suggested?

And does your last sentence mean I should be spraying after harvest until first frost? I'm fairly new to this so that would be helpful information!

Thank you!

I spray with sulfur and haven’t had an issue with my Marquette. You should definitely spray after harvest as you want healthy leaves to store up energy for next year. I’ve made the mistake of not spraying after harvest a couple of times and had downy mildew set me back.

 

[lmshelly]

I spray with sulfur and haven’t had an issue with my Marquette. You should definitely spray after harvest as you want healthy leaves to store up energy for next year. I’ve made the mistake of not spraying after harvest a couple of times and had downy mildew set me back.

Yeah that makes sense...thanks! What do you spray for the several months prior to harvest? I am actually learning the hard way about mancozeb's 66 day PHI... have to forgo harvest this year since I sprayed up through early august.

 

[Cynewulf]

Yeah that makes sense...thanks! What do you spray for the several months prior to harvest? I am actually learning the hard way about mancozeb's 66 day PHI... have to forgo harvest this year since I sprayed up through early august.

You can see some examples from this recent post and let me know if you have any questions:
Disease Identification Advice Please

Also, if you’re not going to use your grapes this year, I’d suggest harvesting them now so the vines can put their energy into preparing for the winter and next year, if you haven’t done it already.

 

[lmshelly]

You can see some examples from this recent post and let me know if you have any questions:
Disease Identification Advice Please

Also, if you’re not going to use your grapes this year, I’d suggest harvesting them now so the vines can put their energy into preparing for the winter and next year, if you haven’t done it already.

Thank you so much. Great advice.

 

[Vern]

You may want to aquire this, Midwest Fruit Pest Management Guide. Available Perdue Education Store , wwwedustore.purdue.edu. a free PDF is also available from the store. This will help you make decisions as to what is needed and when to use. It contains lots of useful information.