Unexplained sudden wilting 3 year old Merlot

[Fox Squirrel Vin]

Heat stress can cause uneven ripening. 115 degrees is HOT and hard on wine grapes. One way to manage heat stress is with water. Making sure they never dry out during the hottest periods is really really helpful. If you are waiting to see drooping tendrils, you are already stressing the plant and it will shut down parts of itself to save other parts. Get a cheap moisture meter rather than waiting to see signs from the plant that it needs water.

Fruit management- Limit the fruit production on young vines to vines closest to the basil wood of the spur, no more than one bunch per vine/spur and no more than 1 linear foot of fruit per 1/4 inch of trunk diameter till the vine is 4-5 years old. Green prune excessive unproductive vines to two buds from the spur or at least down to a 3-4 leaves if your grape producing vines do not have adequate growth (4-5') you can adjust this pruning when the plant is dormant. Excessive growth puts a lot of demand on the plant for sap and in high heat, the plant will struggle with the demand until the trunks are firmly established and are of significant diameter.

Give your vines some triple superphosphate. Phosphorus is involved in several key plant functions, including energy transfer, photosynthesis, transformation of sugars and stimulates root growth. Don't add any nitrogen unless you are seeing vigor issues.

That vine that died really didn't have a robust root structure so factor that with some pest related stress on top of heat related stress on top of a tired vine from producing too much fruit the previous year... You get the picture. Too much environmental stress.

If you are using a backpack sprayer you want to use 1 oz of movento to 4 gallons of water and you need to mix a tablespoon of a non ionic surfactant with it. Dawn dish detergent works in a pinch, I like to use Tween 20 (Polysorbate 20) try to keep it off the fruit, Movento warns about fruit damage from surfactants but focus on spraying the leaves and not the fruit. I like to spray in the evenings before sunset so the evaporation of the water is slower.

 

[balatonwine]

I decided that salvaging one vine is not worth losing the whole vineyard, so the only way to be 100% sure was to dig it up. The good news, is that there is no sign of Phyloxera on the roots that I can tell. The bad news is that the Bermuda grass which has invaded my yard and was growing around the base of this particular vine appears to be weaving it's roots in between the vines. So my theory here is that the Bermuda grass was just stealing too much of the water and nutrients for the Merlot to support it's trunk. That still doesn't explain the healthy vine growth coming from the base, but I don't really know what else it would be at this point.

This and other post comments are interesting, but sadly provide little value. Mainly because this is one plant. Thus one data point. And little to nothing can be extrapolated from one data point.

For example,

1) Bermuda grass: To start off, vines do not like competition in their under canopy root zone. Removing such competition is good practice to help with vine vigor. That being said, I did a multi year trial on a "no till" vineyard, with plenty of Bermuda grass and no vines died. They did have reduced vigor, but no deaths. So solely blaming Bermuda grass may not be accurate. But, again, removing under canopy weeds is a good idea. Many people today reach for some chemical spray. The "better live via chemistry" idea. Great idea in the 1950's for anyone, and still an excuse for Big Ag today. But growing issues are arising. You can decide what is best for you (I will not judge here). But, if you only have 30 vines, after you clear out the Bermuda grass, I might suggest to consider some simple, routine and free of cost mechanical soil tilling is all you need to do to keep your vines weed free and healthier. See video below.

2) Nematodes, etc.... : If you dig up any vine in your vineyard, you may find some root damage. Any wild critter has some disease load. Seeing root damage alone does not prove anything. Some plants may have more root damage than others. But... that maybe simply due to the fact the plant was already weekend for other reasons and can not fend of disease. Thus disease load may be a symptom of other issues that are causing illness, not a direct cause of the illness. Thus the presence or extent of nematodes really can have multiple causes. So is ambiguous.

3) Weak roots: The vine may have started off with a week root system. I have bought many commercial vines and some had very weak roots. I flagged them. And trimmed them to two buds for many years, beyond the trimming what "healthy" plants received. Plants with weak root systems to start need special attention to become healthy adult plants.

Above are just some issues to consider.

Hope this helps.

Weed free vine rows with a wheel hoe:

 

[balatonwine]

I decided that salvaging one vine is not worth losing the whole vineyard, so the only way to be 100% sure was to dig it up. The good news, is that there is no sign of Phyloxera on the roots that I can tell.

I hope you did not dig up your vine simply due to fears of Phyloxera that others may have made here. Because Phyloxera is endemic to the USA and exists pretty much anywhere there are vines. If you have Phyloxera on one vine you have them on all of your vines. Soil types and other mitigating factors allow some areas to remain functionally Phyloxera "free" structurally, and allow native rooted vines to grow mostly healthy (even if some succumb to the louse). So removing and killing one vine out of fear it will "infect others" from Phyloxera will have mostly zero benefit for your vineyard. If the vine was sick due to other issues, especially virus or bacterial disease, then removing it may have been a good idea. But to know that, for certain, you need to send the plant to a lab for analysis. To say otherwise, no amount of forum "experts" pontificating what they think is the problem, or what you should do, based on their pontificates, is not worth a brass farthing.... or the Yankee equivalent: is not worth a damn.... (what is appropriate is depending on which side of the pond one is, and what is the level of censor at forums such as this as to what is appropriate language... ).

 

[Fox Squirrel Vin]

I hope you did not dig up your vine simply due to fears of Phyloxera that others may have made here. Because Phyloxera is endemic to the USA and exists pretty much anywhere there are vines. If you have Phyloxera on one vine you have them on all of your vines. Soil types and other mitigating factors allow some areas to remain functionally Phyloxera "free" structurally, and allow native rooted vines to grow mostly healthy (even if some succumb to the louse). So removing and killing one vine out of fear it will "infect others" from Phyloxera will have mostly zero benefit for your vineyard. If the vine was sick due to other issues, especially virus or bacterial disease, then removing it may have been a good idea. But to know that, for certain, you need to send the plant to a lab for analysis. To say otherwise, no amount of forum "experts" pontificating what they think is the problem, or what you should do, based on their pontificates, is not worth a brass farthing.... or the Yankee equivalent: is not worth a damn.... (what is appropriate is depending on which side of the pond one is, and what is the level of censor at forums such as this as to what is appropriate language... ).

Trying to rejuvenate a vine that has issues when it is so much easier to replace it with a healthy one is not worth the effort, it wasn't a 20 year old plant. He can make plenty of new plants from the plants he has now without worrying about introducing anything from a commercial supplier.

Removing the vine allows you to see into it's past and why it died and what you can improve on. He learned 2 things, the roots were less than sufficient so he needs to focus on methods to improve the root system, and, there looks to be some nematode damage. There is somthing causing his vines to brown and die so these learning experiences can be helpful to keep the rest of his vines thriving and improve on what he is doing. Nematodes are better to be controlled rather than wait until you are infested with them. Then they are much harder to deal with especially in a hot climate and sandy soil where they thrive. Trying to save plants after they have a severe infestation is much more difficult than preventing one.

Improving 2 issues when you may have 5 is a 40% improvement that gives the plant more strength to deal with the other issues it may have and sometimes that is enough. If a plant is healthy below ground it is going to be much healthier above it, Above ground issues are easier to deal with because you can see them.

I do agree with what you are saying but, when a plant has stress from may issues, one single issue may not be enough to kill an otherwise healthy plant but it's enough to kill THAT plant because it is severely stressed due to roots, hot climate, soil pests, too much fruit for its age...

 

[vtoddw]

Heat stress can cause uneven ripening. 115 degrees is HOT and hard on wine grapes. One way to manage heat stress is with water. Making sure they never dry out during the hottest periods is really really helpful. If you are waiting to see drooping tendrils, you are already stressing the plant and it will shut down parts of itself to save other parts. Get a cheap moisture meter rather than waiting to see signs from the plant that it needs water.

Fruit management- Limit the fruit production on young vines to vines closest to the basil wood of the spur, no more than one bunch per vine/spur and no more than 1 linear foot of fruit per 1/4 inch of trunk diameter till the vine is 4-5 years old. Green prune excessive unproductive vines to two buds from the spur or at least down to a 3-4 leaves if your grape producing vines do not have adequate growth (4-5') you can adjust this pruning when the plant is dormant. Excessive growth puts a lot of demand on the plant for sap and in high heat, the plant will struggle with the demand until the trunks are firmly established and are of significant diameter.

Give your vines some triple superphosphate. Phosphorus is involved in several key plant functions, including energy transfer, photosynthesis, transformation of sugars and stimulates root growth. Don't add any nitrogen unless you are seeing vigor issues.

That vine that died really didn't have a robust root structure so factor that with some pest related stress on top of heat related stress on top of a tired vine from producing too much fruit the previous year... You get the picture. Too much environmental stress.

If you are using a backpack sprayer you want to use 1 oz of movento to 4 gallons of water and you need to mix a tablespoon of a non ionic surfactant with it. Dawn dish detergent works in a pinch, I like to use Tween 20 (Polysorbate 20) try to keep it off the fruit, Movento warns about fruit damage from surfactants but focus on spraying the leaves and not the fruit. I like to spray in the evenings before sunset so the evaporation of the water is slower.

Thank you again for your invaluable feedback, I'm learning a ton here!

Fortunately 115 is not the average, it's usually between 90 and 104 here during any given summer day, but coincidentally the last two Labor Days were record breakers, not exactly trending in a good direction.

Right now I'm deep watering my vines 2 gallons of water per vine twice a week via a slow drip line on a regular timer. I'm watching the tendrils and the color of the leaves to ensure I'm not over or under watering and they seem to be doing well at the moment. When it gets hotter, in May or June I'll likely increase that to 4 gallons per vine twice a week. My biggest takeaway from last year, during which I was initially watering once a week with 2 gallons per vine, was that although they may look fine in the spring on the average days, the vines will need extra water on the above average hot days, so it's not a just a passive process where I set the timer and wait for harvest.

I also learned last year by researching the leaf burning and discoloration on my Zinfandel that they appeared to be lacking in Phosphorus, so now that you corroborated that I feel much better (as I was thinking it was Pierce's disease - which it still could be, we'll see) so back in late February just before bud break I gave the 5 mature Zinfandel vines (excluding the newly planted vine) 2 tbsp of "Easy Peasy Super Phosphate" 60% 0-46-0 Phosphorus and worked it into the soil and soaked for a while. Unfortunately the bag doesn't have explicit instructions for Grapes so I had to guess how much based on it's broad recommendation and stayed on the low side as I don't want to kill the vines. I also gave all mature vines (none of the 1st years) 1/2 to 1 cup (depending on trunk diameter) of Dr Earth 5-5-2 the start of April. I also read that I should limit the nitrogen unless the vine is low vigor, whereas the last several years I just gave all mature vines a shot of the 5-5-2 every 2 months during the growing season as the directions on the bag say, which once again I found to be counter to conventional wisdom. So my plan now is to watch the vines and only give them more fertilizer as needed, although given some of the stunted shoots on a few of the Zinfandel vines maybe that time is now.

Yeah that makes a lot of sense, too many factors just overworked the vine and killed it. For reference, here's how the row of Zinfandel looked at the end Labor Day weekend 2020. The closest to the camera is still alive and producing, but it does have stunted shoots and several buds that never broke this year. The second from the camera is the one that was fully dead by spring 2021. I harvested everything that weekend prematurely because the heat basically destroyed the vines and much of the grapes. Here's a picture of what it did to some of the grapes that we're a nice dark purple just days before.

 

[vtoddw]

This and other post comments are interesting, but sadly provide little value. Mainly because this is one plant. Thus one data point. And little to nothing can be extrapolated from one data point.

For example,

1) Bermuda grass: To start off, vines do not like competition in their under canopy root zone. Removing such competition is good practice to help with vine vigor. That being said, I did a multi year trial on a "no till" vineyard, with plenty of Bermuda grass and no vines died. They did have reduced vigor, but no deaths. So solely blaming Bermuda grass may not be accurate. But, again, removing under canopy weeds is a good idea. Many people today reach for some chemical spray. The "better live via chemistry" idea. Great idea in the 1950's for anyone, and still an excuse for Big Ag today. But growing issues are arising. You can decide what is best for you (I will not judge here). But, if you only have 30 vines, after you clear out the Bermuda grass, I might suggest to consider some simple, routine and free of cost mechanical soil tilling is all you need to do to keep your vines weed free and healthier. See video below.

2) Nematodes, etc.... : If you dig up any vine in your vineyard, you may find some root damage. Any wild critter has some disease load. Seeing root damage alone does not prove anything. Some plants may have more root damage than others. But... that maybe simply due to the fact the plant was already weekend for other reasons and can not fend of disease. Thus disease load may be a symptom of other issues that are causing illness, not a direct cause of the illness. Thus the presence or extent of nematodes really can have multiple causes. So is ambiguous.

3) Weak roots: The vine may have started off with a week root system. I have bought many commercial vines and some had very weak roots. I flagged them. And trimmed them to two buds for many years, beyond the trimming what "healthy" plants received. Plants with weak root systems to start need special attention to become healthy adult plants.

Above are just some issues to consider.

Hope this helps.

Weed free vine rows with a wheel hoe:

Given your experiment that certainly implies that the Bermuda grass is a problem, but not the singular cause. Good to know and I'm glad you clarified that especially for anyone reading this thread as it's important that writing this off as a Bermuda Grass problem is not how we left it given that per your experience it's likely not the only factor.

In hind sight, I think the weak roots is likely a big issue for me, as I really have been progressively learning over the years from books and google searches, but I've never taken the time to seek assistance until now. When it comes to the information I've read, it's often incomplete leaving gaps or it's too circumstantial. For example, I've read that vines need deep watering and should dry out, so should only be watered once a week. Then in practice, as indicated in my prior post, that was not sufficient for every day. I've also read that once a vine is established, it doesn't need any water at all as it's roots will get it from ground water, but based on past experiences I'm fairly confident that if I turn off my irrigation for the next two weeks all of my 6 and 7 year old vines will die. It really is hard to know who and what to believe, because the fast is it all depends on a lot of environmental factors.

So the way I imagine that translates to weak roots is that I've been underwatering the vines for years and possibly not giving them the right nutrients (I know that for sure with the Zinfandel at least). Also in regards to the weeds, I do use a cultivator in the late winter around pruning time, although I'm admittedly timid with it as I don't want to go to deep and damage the vine roots, but maybe I'm too timid as the vine roots do tend to grow downward as I've discovered from the one I pulled.

The other piece of info of note here is that when you look at the 3 vines in the same row on either side of the one I pulled, they are (for now) doing great. This vine I dug up has always been low vigor but was planted the same year (spring of 2018) as the other 3, all from the same nursery. Come to think of it there is another vine in that row which also has had consistently low vigor, shown in picture 154114 here.

 

[vtoddw]

I hope you did not dig up your vine simply due to fears of Phyloxera that others may have made here. Because Phyloxera is endemic to the USA and exists pretty much anywhere there are vines. If you have Phyloxera on one vine you have them on all of your vines. Soil types and other mitigating factors allow some areas to remain functionally Phyloxera "free" structurally, and allow native rooted vines to grow mostly healthy (even if some succumb to the louse). So removing and killing one vine out of fear it will "infect others" from Phyloxera will have mostly zero benefit for your vineyard. If the vine was sick due to other issues, especially virus or bacterial disease, then removing it may have been a good idea. But to know that, for certain, you need to send the plant to a lab for analysis. To say otherwise, no amount of forum "experts" pontificating what they think is the problem, or what you should do, based on their pontificates, is not worth a brass farthing.... or the Yankee equivalent: is not worth a damn.... (what is appropriate is depending on which side of the pond one is, and what is the level of censor at forums such as this as to what is appropriate language... ).

Well yes and no, the feedback I received did encourage me to pull the vine but I came to the conclusion on my own based on the cost vs benefit of keeping it or removing it. From what I've been reading you do have a point that it was likely too late if it was Phyloxera, but I also needed to know if it was something else that posed an avoidable risk to the rest of the vines. Some of these vines are actually 6 and 7 years old, so I'd rather not lose them too for the sake of one low-vigor vine that may or may not die by the end of the summer anyway. I have yet to take the step of actually sending my soil or vines to a lab for analysis, but if things continue to worsen this season then maybe that's my next move. In the grand scheme of things, I'll still make wine this year by buying grapes from local growers, but I've put a lot of time, money and effort into my little vineyard so ideally I'd like to get a meaningful return out of it.

 

[Fox Squirrel Vin]

Thank you again for your invaluable feedback, I'm learning a ton here!

Fortunately 115 is not the average, it's usually between 90 and 104 here during any given summer day, but coincidentally the last two Labor Days were record breakers, not exactly trending in a good direction.

Right now I'm deep watering my vines 2 gallons of water per vine twice a week via a slow drip line on a regular timer. I'm watching the tendrils and the color of the leaves to ensure I'm not over or under watering and they seem to be doing well at the moment. When it gets hotter, in May or June I'll likely increase that to 4 gallons per vine twice a week. My biggest takeaway from last year, during which I was initially watering once a week with 2 gallons per vine, was that although they may look fine in the spring on the average days, the vines will need extra water on the above average hot days, so it's not a just a passive process where I set the timer and wait for harvest.

I also learned last year by researching the leaf burning and discoloration on my Zinfandel that they appeared to be lacking in Phosphorus, so now that you corroborated that I feel much better (as I was thinking it was Pierce's disease - which it still could be, we'll see) so back in late February just before bud break I gave the 5 mature Zinfandel vines (excluding the newly planted vine) 2 tbsp of "Easy Peasy Super Phosphate" 60% 0-46-0 Phosphorus and worked it into the soil and soaked for a while. Unfortunately the bag doesn't have explicit instructions for Grapes so I had to guess how much based on it's broad recommendation and stayed on the low side as I don't want to kill the vines. I also gave all mature vines (none of the 1st years) 1/2 to 1 cup (depending on trunk diameter) of Dr Earth 5-5-2 the start of April. I also read that I should limit the nitrogen unless the vine is low vigor, whereas the last several years I just gave all mature vines a shot of the 5-5-2 every 2 months during the growing season as the directions on the bag say, which once again I found to be counter to conventional wisdom. So my plan now is to watch the vines and only give them more fertilizer as needed, although given some of the stunted shoots on a few of the Zinfandel vines maybe that time is now.

Yeah that makes a lot of sense, too many factors just overworked the vine and killed it. For reference, here's how the row of Zinfandel looked at the end Labor Day weekend 2020. The closest to the camera is still alive and producing, but it does have stunted shoots and several buds that never broke this year. The second from the camera is the one that was fully dead by spring 2021. I harvested everything that weekend prematurely because the heat basically destroyed the vines and much of the grapes. Here's a picture of what it did to some of the grapes that we're a nice dark purple just days before.

When it starts warming up for you, try keeping the soil damp at all times and do light cultivation where you think the roots end. That will help keep the soil soft and the phosphate will encourage growth. It's ok if you cut some of the small roots in tilling because that encourages more root growth.

It's really not true that the soil should dry or it isn't good for the plant, I live in Florida and all growing season when the plants have fruit, my soil is moist and in August the water table is 18 inches below the surface and there are periods where it is saturated and they do fine. A lot of grape regions in France have substantial rains during the fruit ripening stage. When I water during a dry spell I have my drip set to deliver 2 gallons every 2 days. You don't need to increase how much water you are giving them when it's hot, you need to increase the frequency. 4 gallons accomplishes the same as two because that excess water just seeps deep into the soil where there are no roots and isn't available to the plant.

If I am going to give them nitrogen, I do it in spring at bud formation, If the plant looks light on buds or they seem to be growing slow I give them nitrogen because I want good, excessive fruit bearing shoots that I can prune back after I see the quality of the fruit bunches/clusters that form on them rather than shoots with no fruit. This method lets me choose the best vines with the best fruit and I can prune the clusters that are sparse and poor quality. All they do is increase the demand on the plant and steal from the clusters that I want to perform the best. A good 10-10-10 fertilizer is ideal at this stage. Get your fertilizer from a good garden center, fertilizer from big box stores is usually crap. I will also do a micro nutrient foliar spray just after fruit set, I use a product the citrus growers use, this just helps to make sure the plans have everything they need to get off to a good start before the heat of summer sets in.

You look like you are in an arid climate so I'm not sure what your fungus pressure is like but I spray 7 different fugicide groups alternating every 14 days. I have no choice, It's Florida. I spend thousands of dollars on fungicides every year, not just on the grapes but all the crops. The fungus pressure here is intense.

 

[vtoddw]

When it starts warming up for you, try keeping the soil damp at all times and do light cultivation where you think the roots end. That will help keep the soil soft and the phosphate will encourage growth. It's ok if you cut some of the small roots in tilling because that encourages more root growth.

It's really not true that the soil should dry or it isn't good for the plant, I live in Florida and all growing season when the plants have fruit, my soil is moist and in August the water table is 18 inches below the surface and there are periods where it is saturated and they do fine. A lot of grape regions in France have substantial rains during the fruit ripening stage. When I water during a dry spell I have my drip set to deliver 2 gallons every 2 days. You don't need to increase how much water you are giving them when it's hot, you need to increase the frequency. 4 gallons accomplishes the same as two because that excess water just seeps deep into the soil where there are no roots and isn't available to the plant.

If I am going to give them nitrogen, I do it in spring at bud formation, If the plant looks light on buds or they seem to be growing slow I give them nitrogen because I want good, excessive fruit bearing shoots that I can prune back after I see the quality of the fruit bunches/clusters that form on them rather than shoots with no fruit. This method lets me choose the best vines with the best fruit and I can prune the clusters that are sparse and poor quality. All they do is increase the demand on the plant and steal from the clusters that I want to perform the best. A good 10-10-10 fertilizer is ideal at this stage. Get your fertilizer from a good garden center, fertilizer from big box stores is usually crap. I will also do a micro nutrient foliar spray just after fruit set, I use a product the citrus growers use, this just helps to make sure the plans have everything they need to get off to a good start before the heat of summer sets in.

You look like you are in an arid climate so I'm not sure what your fungus pressure is like but I spray 7 different fugicide groups alternating every 14 days. I have no choice, It's Florida. I spend thousands of dollars on fungicides every year, not just on the grapes but all the crops. The fungus pressure here is intense.

Yeah it's very arid here, we don't get much rain at all so irrigation is always necessary. Right now my watering is every Monday and Friday so I really never let them dry out much, except maybe by Thursday, but that makes sense that doubling the water per day doesn't necessarily mean the plant can actually absorb it all before it dissipates in the soil, so maybe I'll try out every 2 days when it starts getting hotter and watch the leaves for signs of overwatering. I'll also take you advise and do some extra cultivation, that's a good idea. The fertilizer I've been using it from Armstrong nursery, so I'm not sure where it lays on the spectrum, but it's definitely not Home depot / Lowes so maybe it's decent stuff. But again it's 5-5-2 fruit / vine fertilizer, not really specified for grape growing so I'll seek out some 10-10-10 and give that a shot. I also only gave the Zinfandel row the extra Potassium, but I'm thinkin maybe I should have done that for the whole vineyard as I imagine they are all depleting their nutrients at a fairly relative rate.

I actually just went up there today and cluster thinned everything down to the one cluster closest to the basil per spur because most of the grapes are flowering right now and I've read that you want to do your cluster thinning before fruit set to get the best quality (no clue if that's true). I also broke off several of the shoots that were stunted and didn't offer a good bud position for next year or that were vigorous but blocked the sunlight on the clusters excessively.

In terms of fungus, even as hot and dry as it is out here, I've had Powdery Mildew on a 2 of my oldest vines the last 2 years, plus what I believe is Grapevine Leaf Rust on some of the older one's as well but I'm not 100% sure about the latter. My planned spraying schedule is using "Bonide Sulfur Fungicide Dust" every 2 weeks for the first 10 weeks of the growing season. That said, I've skipped the last spray (which would have been last weekend) because I released a bunch of Green Lacewing larva on the grapes in order to eat any of the possible sharpshooter eggs last Wednesday, so I didn't want to kill them with the Sulfur just incase they are sensitive to it. I also spray the fungicide at night because it's just way too hot during the day and as I understand it will damage the plants if sprayed during heat above 85F, not to mention it's easier on me as well, but I really need to get back out there and spray next week as I'm definitely overdue.

I was using an oil based fungicide in prior years but purchased the Sulfur Dust last year in response to the fact that although the Powdery mildew stayed in check, I started seeing what appears to be grape leaf rust show up, which the oil based fungicide did not say it was effective against.

Here's a pic of what I believe is likely Grape Leaf Rust.

 

[Fox Squirrel Vin]

From today

Yeah it's very arid here, we don't get much rain at all so irrigation is always necessary. Right now my watering is every Monday and Friday so I really never let them dry out much, except maybe by Thursday, but that makes sense that doubling the water per day doesn't necessarily mean the plant can actually absorb it all before it dissipates in the soil, so maybe I'll try out every 2 days when it starts getting hotter and watch the leaves for signs of overwatering. I'll also take you advise and do some extra cultivation, that's a good idea. The fertilizer I've been using it from Armstrong nursery, so I'm not sure where it lays on the spectrum, but it's definitely not Home depot / Lowes so maybe it's decent stuff. But again it's 5-5-2 fruit / vine fertilizer, not really specified for grape growing so I'll seek out some 10-10-10 and give that a shot. I also only gave the Zinfandel row the extra Potassium, but I'm thinkin maybe I should have done that for the whole vineyard as I imagine they are all depleting their nutrients at a fairly relative rate.

I actually just went up there today and cluster thinned everything down to the one cluster closest to the basil per spur because most of the grapes are flowering right now and I've read that you want to do your cluster thinning before fruit set to get the best quality (no clue if that's true). I also broke off several of the shoots that were stunted and didn't offer a good bud position for next year or that were vigorous but blocked the sunlight on the clusters excessively.

In terms of fungus, even as hot and dry as it is out here, I've had Powdery Mildew on a 2 of my oldest vines the last 2 years, plus what I believe is Grapevine Leaf Rust on some of the older one's as well but I'm not 100% sure about the latter. My planned spraying schedule is using "Bonide Sulfur Fungicide Dust" every 2 weeks for the first 10 weeks of the growing season. That said, I've skipped the last spray (which would have been last weekend) because I released a bunch of Green Lacewing larva on the grapes in order to eat any of the possible sharpshooter eggs last Wednesday, so I didn't want to kill them with the Sulfur just incase they are sensitive to it. I also spray the fungicide at night because it's just way too hot during the day and as I understand it will damage the plants if sprayed during heat above 85F, not to mention it's easier on me as well, but I really need to get back out there and spray next week as I'm definitely overdue.

I was using an oil based fungicide in prior years but purchased the Sulfur Dust last year in response to the fact that although the Powdery mildew stayed in check, I started seeing what appears to be grape leaf rust show up, which the oil based fungicide did not say it was effective against.

Here's a pic of what I believe is likely Grape Leaf Rust.

Don't use the oils, they harm the plants at temps above 85 degrees, sulfur can also cause injury at temps over 85.

https://doubleavineyards.com/news/2012/10/19/sulfur-injury-on-grapevines/

 

[balatonwine]

Trying to rejuvenate a vine that has issues when it is so much easier to replace it with a healthy one is not worth the effort, it wasn't a 20 year old plant. He can make plenty of new plants from the plants he has now without worrying about introducing anything from a commercial supplier.

I agree. But....

Removing the vine allows you to see into it's past and why it died and what you can improve on.

This is one data point. Nearly impossible to learn much from one event.

He learned 2 things, the roots were less than sufficient so he needs to focus on methods to improve the root system, and, there looks to be some nematode damage.

I do agree there are indicators to improve the root system, but is far more complicated than only "2 things". As I already stated, presence of nematode damage is inconclusive. Such damage maybe causal causing the vine's decline, or relative and simply a symptom of damage to a weekend vine. To confirm one or the other, we need to ask the OP to pull up many healthy vines and compare nematode loads. Healthy vines can actually sustain quite a lot of root damage. So we would need to compare. I doubt he will do that. Even so... it is still an issue of maybe confusing correlation and cause and effect.

And do not get me started on my opinions of the issues root quality of irrigated versus not irrigated vineyards.....

Improving 2 issues when you may have 5 is a 40% improvement

Where did you pull those numbers from? 40%???

It sounds like the saying, 90% of comments here are false. And the rest are simply wrong. (i.e. if you use %, be prepared to quote authoritarian sources, or willing to admit your % is made up....)

Note: Made a few edits to my post. The one at 17:45 my time (CET) is my last edit and the one to reply to.

 

[vtoddw]

From today

Don't use the oils, they harm the plants at temps above 85 degrees, sulfur can also cause injury at temps over 85.

https://doubleavineyards.com/news/2012/10/19/sulfur-injury-on-grapevines/

Great article, nice to see an explanation as to why the bag says not to apply above 85F. Yeah I've stopped using the oil because it said it was only effective against powdery mildew, hence the grape leaf rust. It was effective on powdery mildew as a corrective measure, rather than just preventive, which was nice, but as long as I'm staying on top of the Sulphur spraying I should be good.