Disease Identification Advice Please

[Jim in Tennessee]

Good Morning All
I have a small vineyard in East Tennessee planted with Enchantment grapes. I selected this variety for it's disease resistance.

I have vines with this coloration that is spreading. I presume it is fungus related due to our recent rains and humidity.

I sprayed Captan yesterday, but need to confirm what this is before proceeding to another fungicide (Mancozeb or Myclobutanil). Any other suggestions?

Thanks for your help.

 

[Dustyfj]

I’ll defer to more experienced growers, but that looks like efficacy from your captain spray. All the mold/disease dies but infected leaf surface gets damaged from the spray. You must have had an emergency downy/powdery event. Saves the plant but doesn’t look pretty.

 

[Cynewulf]

It’s a little hard to tell from your photos as they’re pretty low resolution. It looks like there could be downy mildew if there’s fuzzy growth on the underside of the leaves. What is your spray protocol? Mancozeb and myclobutanil are preventative rather than curative. It will help prevent future infections but won’t fix what you have (if it’s actually a fungal infection). If it’s downy you might try spraying with phosphorus acid, which has some kick-back properties.

I have a few Enchantment left and they are probably the most disease resistant of my vines. That said, they’re also the strangest in terms of vigor, growth habit, and around this time of year their leaves often do strange things; enough to the point that I just ignore it now. Even the photo on Double A Vineyard’s Enchantment page has some discoloration similar to yours. Here is what mine looks like right now:




I spray them the same as the rest of my grapes, though they probably don’t need as much. I started with 13 vines and think I’m down to about 5 or 7 now. I’ve replaced several because they’re just so slow growing in my vineyard compared to my other varieties but I understand others haven’t had the same issue. The grapes are very nice with beautiful clusters, great chemistry and nice tannins for a hybrid.

 

[Jim in Tennessee]

Thanks Dustyfj and Cynewulf.

The picture in my post was prior to spraying with Captan. I contacted our local UT Ag rep and he suggested that it is probably black rot. I sprayed Mancozeb on Friday to stop any additional fungal growth.

The vines had been very vigorous until we had a lot of rain. I will need to do a follow-on spray soon.
Fungus has been horrible on everything here in NE Tennessee during the past month.

This is my first vineyard, so I selected Enchantment based on disease resistance in this climate, but I neglected to do any preventive spraying since I saw no disease at all until the rains came. Big mistake, obviously.
Thanks again.
Jim

 

[Cynewulf]

Thanks Dustyfj and Cynewulf.

The picture in my post was prior to spraying with Captan. I contacted our local UT Ag rep and he suggested that it is probably black rot. I sprayed Mancozeb on Friday to stop any additional fungal growth.

The vines had been very vigorous until we had a lot of rain. I will need to do a follow-on spray soon.
Fungus has been horrible on everything here in NE Tennessee during the past month.

This is my first vineyard, so I selected Enchantment based on disease resistance in this climate, but I neglected to do any preventive spraying since I saw no disease at all until the rains came. Big mistake, obviously.
Thanks again.
Jim

I made the same mistake my first year. I didn’t spray because I follow a lot of natural winemakers in France and everything looked great for a while, but realized by mid summer I couldn’t do that in Virginia. I lost the first round of foliage to black rot, then the secondary leaves were eaten by Japanese beetles. I have a solid preventative spray protocol I follow now and am generally happy with the health of my vines, though every year seems to bring a completely new challenge.

 

[Jim in Tennessee]

Thank you very much.
Would you mind sharing your preventative spray protocol? I might add, these are new vines that I planted in April of this year.
Thanks again.

 

[Cynewulf]

Here are a couple of example schedules. I more or less follow the one titled Fungicide Schedule 1, though modified a little as I’ve added Immunox after I’ve completed my 6 applications of mancozeb for the season, and also use BT for caterpillars and phosphorus acid sometimes for downy if there have been heavy rains. I have Cabernet Franc, Petite Sirah, Marquette, Itasca, Enchantment, Regent, and Chelois. Each has a different level of disease susceptibility but I generally spray them all the same for the sake of simplicity and end up with about 15 total spray applications, including the post harvest sprays. You may be able to get away with a much reduced schedule for Enchantment.

 

[Jim in Tennessee]

Thank you very much!

 

[Hazelemere]

It looks like potassium deficiency (red leaf colour) . Foliar spray with a solution of potassium bicarbonate say 1/4 cup in 2 gallons of water may fix it. Potassium bicarbonate may also be antifungal without the need for synthetic fungicides.

 

[Jim in Tennessee]

Hazelemere:
Thank you for your response. I will look into this as well.