Newbie with black-rotted vine - what to do

[Salinity]

Hi all - we recently purchased a home with 2 large and not well maintained grapevines of unknown variety (in RI). When I say large, I mean one trellis is pretty much a canopy 12 x 10 (actually looks to be 2 stems) and the other is a half-arc along a fence about 8 feet high and 10 feet long.

Both vines are showing obvious signs of black rot all over the vines (not localized to one particular part of the vine). The vines are also certainly unwieldy and frankly, I can't tell what shoot is coming from what lead or stem, etc. I tried thinning it out a bit, but it's still a crazy mess and I didn't really know what I was doing, since I couldn't count leaves, etc. We would like to harvest good grapes from these vines eventually (we were told the Portuguese families around know these vines well and may come over to take excess grapes for wine making - we want to try that out ourselves!).

At this point, what should my plan be? I've read I should remove infected leaves and clusters, but that's basically all of them. Should I just concentrate on the clusters or just the leaves? Should we wait until fall / winter and hack these back quite a bit? Thanks in advance for any advice.

 

[balatonwine]

Once parts of leaves and fruit have black rot, they have black rot. You can not undo it. But you can prevent further infection.

But quite frankly, advice to remove infected leaves is only correct if a few leaves or fruit are affected. Else, let the plant take care of the issue, with a little help from you.

First off, you can help protect those parts of the plant that are not yet infected. And this is rather important. So I would start by spraying any appropriate anti-black rot fungicide on your vines ASAP. And keep up the application frequently for the next few months. Vines will grow new leaves all summer. Those that are affected now may eventually self lysis and fall off, but they will be replaced by new young leaves. You want to keep those new young leaves treated so they do not also get black rot.

And many leaves that have black rot may sill produce enough production for the plant that they will remain and overall benefit the plant.

As for the grapes, they may be unusable. But again, it is a matter of degree. Some may be infected, but others may not be. For full cluster infection, yes I would cut them off as leaving them on just waste the vine's energy on a trying to ripen something that will never properly ripen. Let that energy rather be placed into the vine's overall health to make it through this infection. But if a cluster is only partially infected, try to just cut off the infected part. You may not be able to make wine from the fruit, but maybe some jams or jellies.

 

[Salinity]

Great - thanks. I started removing obviously infected clusters and sections of the vine (leaves and shoots) - when doing so, should I cut back the entire shoot to the cane (I think I have that terminology right), or just remove leaves and infected clusters? There certainly is a lot of new growth. I'll look into an anti-black rot fungicide as well.

Cheers!

 

[Karl]

Jason - question here. Why do you think it is black rot? From my experience black rot rarely affects the leaves, typically just the grape clusters. There should be no reason necessary to remove entire canes unless the entire cane is dying. Could it be Anthracnose? Phomopsis?

Spraying vines that large also posses a problem. Picking a few good sprays is one thing, but applying the spray can be tricky if the vines are as large as you say.

 

[salcoco]

it should be noted that any spray for black rot has a "stop before harvest date" of about 60 days If I remember correctly. something to check before spraying;. also if black rot once grapes start to ripen spaying is not necessary as disease does not affect these grapes. I would suggest save your efforts to next year. record your beginning of veraison, the ripening of the grapes and harvest dates. wait util plant is dormant and in early spring prune the plants to a good shape. burn all residue as black rot spores will be still in the plant residue. also clean everything around the plans, dead leaves etc. obtain spray chemicals for mildew and black rot commence spaying once shots reach 3 inches long every 10 days there after , more often if rainy weather. check with your local county extension office they should be able to help with spray program and sources for chemicals.

 

[user 36973]

Why do you think it is black rot? From my experience black rot rarely affects the leaves, typically just the grape clusters

Ditto. Black rot only infects grapes. I usually see a purple spot form from the underside of the grape and it winds its way up the grape and shrivels it.

If you are seeing leaves/canes affected, you should investigate whether you have downy mildew, which is what I'd bet you are seeing. At this point in the season, you can spray Captan as a preventative spray, Rampart as a corrective spray and Rally as a systemic spray to protect from further damage. These are all 14-day PHI or less. Earlier in the season you could have sprayed mancozeb, but that has a 66 day PHI.

 

[balatonwine]

Ditto. Black rot only infects grapes. .

Incorrect. Most economic damage does occur on fruit. But leaves can also be affected.

This site shows this photo and others of black rot damage on leaves:

http://www.omafra.gov.on.ca/IPM/english/grapes/diseases-and-disorders/black-rot.html

 

[balatonwine]

also if black rot once grapes start to ripen spaying is not necessary as disease does not affect these grapes. I would suggest save your efforts to next year.

There is no help for any infected fruit now, true. But spraying now can still protect some fruit till veraison and will protect new leaf growth, if black rot conditions persist (because most certainly those conditions are excellent for other fungus pathogens). Protecting leaf growth helps the plant build wood and reserves for next year. You have to think of the plant's long term health, not just this years grape harvest. Liquid lime sulfur can be sprayed up to 30 days prior to harvest as a moderate assistance for late season black rot and other diseases, but not all (loss of leaves as described by the OP may lean more toward downy mildew -- then use Bordeaux Mix (also 30 days pre-harvest) or similar or better rated fungicide).

 

[FrontenacMan]

I've been doing a bit of research on black rot. The biggest preventative seems to be proper vineyard management. That being pruning discipline and managing moisture and surrounding soil etc. The fungus explodes and spreads in hot moist conditions and is most damaging during bud break when vines are most susceptible. This is the only point that fungicides can help to prevent infection. As the grapes begin to grow and the skins thicken they are less susceptible but certainly not immune. Everything I've read says keep air flow as much as possible to keep new growth dry. Also sterilize your pruning equipment as you can spread the fungus in this manor. The area I am in has had a very warm wet spring which are ideal conditions for black rot. In addition, it is important to remove the "mummified" fruit as it overwinters the spores and then releases them next year in spring when temperatures rise.

 

[Masbustelo]

Balaton How do you keep micronized sulfur from clogging the spray tips? Im using a backpack sprayer. Or does anyone else have suggestions? I think I have a #8 mesh tip.

 

[Dennis Griffith]

This late in the season you may want to try something like Serenade. It's a biological fungicide and can be used up to 1 day before harvest. This may help you get thru the season so that you can start next season early with the right mix. Has the fruit started veraisin yet?

 

[Dennis Griffith]

it should be noted that any spray for black rot has a "stop before harvest date" of about 60 days If I remember correctly. something to check before spraying;. also if black rot once grapes start to ripen spaying is not necessary as disease does not affect these grapes. I would suggest save your efforts to next year. record your beginning of veraison, the ripening of the grapes and harvest dates. wait util plant is dormant and in early spring prune the plants to a good shape. burn all residue as black rot spores will be still in the plant residue. also clean everything around the plans, dead leaves etc. obtain spray chemicals for mildew and black rot commence spaying once shots reach 3 inches long every 10 days there after , more often if rainy weather. check with your local county extension office they should be able to help with spray program and sources for chemicals.

Don't forget to clean your tools with bleach water.

 

[Salinity]

Ditto. Black rot only infects grapes. I usually see a purple spot form from the underside of the grape and it winds its way up the grape and shrivels it.

If you are seeing leaves/canes affected, you should investigate whether you have downy mildew, which is what I'd bet you are seeing. At this point in the season, you can spray Captan as a preventative spray, Rampart as a corrective spray and Rally as a systemic spray to protect from further damage. These are all 14-day PHI or less. Earlier in the season you could have sprayed mancozeb, but that has a 66 day PHI.

Sorry for the lack of response - summer got away from me. Here are some photos of the leaves / early clusters and why I thought blackrot. Seemed to match visually a lot of the descriptions I've seen. At this point I'm aiming to do some proper fall / winter maintenance, as the vines are a bit crazy. We did get some decent grapes (not sure what varietal) but they lacked a good sugar content.

 

[Karl]

Black rot IMO usually effects the entire cluster, and very quickly, so you would have seen entire clusters of mummies later in the season. Individual grapes like in your pictures could really be anything, and at this stage of the season i would just do some research the plan a proper spray program for next spring. Depending on the grape variety, you have several options. Any idea what kinds of vines these are....judging by the size you described they don't sound like vinifera wine grapes at all.

 

[Dennis Griffith]

Ditto. I would get the soil tested and the leaves/petioles as well. This could be caused by a nutrient/mineral deficiency. The soil test will tell what's below as the plant test will tell you what the plants uptake is.

 

[Salinity]

Black rot IMO usually effects the entire cluster, and very quickly, so you would have seen entire clusters of mummies later in the season. Individual grapes like in your pictures could really be anything, and at this stage of the season i would just do some research the plan a proper spray program for next spring. Depending on the grape variety, you have several options. Any idea what kinds of vines these are....judging by the size you described they don't sound like vinifera wine grapes at all.

Really don't know what kind of vines they are - the grapes had seeds and the skins were pretty tough, but that's really all I have to go on. The former owner said these vines were well-known among the local Portuguese families, as they liked to come over and pick them, presumably for wine. Here's a picture of a couple clusters from the summer (kind of hard to see)

 

[Karl]

Guessing some type of American grape, similar to Concord. How did they taste?? Vinifera is unlikely given your location and appearance of the grapes, size of the vine. You could visit the Double A Vineyard website and take a look at their (large) selection of American vines for sale. Maybe one will stand out.