What is wrong with my grapes

[GreginND]

I'm seeing this on some of my Frontenac blanc. I haven't seen it before. We've been quite cool but not freezing. Could it be cold damage or is this a disease problem?

 

[mfzona]

The edges of the leaves in the second picture look like typical 2,4D damage. Any weed spraying going on around the vines?

 

[GreginND]

I think the leaves are just young and unfurling. I'm more concerned about the dried up black leaves. It doesn't look like typical 2,4-D damage and the crops around us have only just been planted. I don't think they sprayed. I'm a bit worried about 2,4-D and Dicamba ready soybeans. Would they spray before planting?

 

[mfzona]

They could spray before planting, but usually that's with glyphosate. Not sure about pre-plant spraying using 2,4D.

 

[fivebk]

If they no-till farm they could spray when planting to kill all plants already growing. They do it here in Iowa!

 

[fivebk]

I'm not sure it's 2-4-D but it kills everything

 

[fivebk]

Could you have got a very lite frost??

 

[GreginND]

Definitely not no-till here. And it is possible with the cold wet winds we had there could have been some cold damage even if the reported temps did not go down too low.

 

[grapeman]

Have you applied a fungicide yet? The damage looks similar to some phomopsis infection. I don't see a lot of stem damage yet but some looks to be there. The look of the leaves looks a lot like phomopsis foliar damage. There are a number of effective sprays for phomopsis and black rot. It could be some type of herbicide damage but I am not convinced yet.

 

[GreginND]

I am about to start with mancozeb this week.

 

[grapeman]

That could be the problem then Greg. Phomopsis and black rot are both early developing diseases when not sprayed early enough. Generally when shoots reach 3-5 inches you should begin a protective program. It is easier to prevent than eliminate later. Even if that isn't what those vines have you will still benefit from the spraying.

 

[garymc]

Probably not relevant to this plant problem, but 2, 4-D is a broadleaf weed killer. It doesn't kill everything. That's why you can spray it on your lawn and it kills the dandelions and plantain, etc, but not the grass. It can also be sprayed on wheat (wheat is a grass) to kill broadleaf weeds. Grapes, being broadleaf plants are affected by it and are very sensitive to it.

 

[GreginND]

Thanks. I think you are right. I did see some of the cane spots characteristic of phomopsis last year. I'll begin spraying asap and make sure to get a good jump start on spraying next year.

 

[BigH]

Greg,

Something like this hit my frontenac and frontenac blanc in spring of 2016 when shoots were about 6 inches long. Many of my shoot tips just blackened up and fell off. Univerisity extension said it was probably anthracnose based on my description and what they saw in my area. They recommended liquid lime sulfur (nasty stuff) before bud break. I followed their advice this year and whatever it was did not return

Frontenac is not supposed to be very susceptible to either phomopsis or anthracnose. Go figure.
H

 

[GreginND]

Thanks. Our university tested them and couldn't find anthracnose. The vines have recovered just fine so I think it was cold and wind damage.