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Sustainable Winegrowing with Vineyard Team

Sustainable Winegrowing with the Vineyard Team brings you the latest in science and research for the wine industry. This on-the-go, sustainable farming educational resource provides in-depth technical information on topics like integrated pest management, fruit quality, water conservation, and nutrient management from experts like Dr. Mark Fuchs of Cornell University, Dr. Michelle Moyer of Washington State University, Cooperative Extension Specialists, veteran growers, and more. Our podcasts will help you make smarter, sustainable vineyard management decisions to increase efficiency, conserve resources, and maximize fruit quality.

May 19, 2022

All winegrowers are on the same quest to find virus negative plant material. James Stamp, President at Stamp Associates Viticulture, Inc, works with his clients to find the highest quality grapevine plants to establish new vineyards. This thorough process to find virus negative material includes partnering with nurseries that previously delivered good product. There is oversight through all stages of production from testing material to harvesting and grafting, from production to delivery, and the final selection of plants for the vineyard site. The number one tip to get quality grapevines is to pay attention to where the plant material is coming from, have great communication with the nursery, and sample the finished product for Red Blotch and Leaf Roll Three.


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Craig Macmillan  0:00 

My name is Craig Macmillan and I am your host, as always. Today we have with us James Stamp, who is president of Stamp Associates Viticulture, Incorporated. And thanks for being on the show, James. I'm really looking forward to this.


James Stamp  0:13 

Yes, thanks for having me, Craig, I'm looking forward to it as well.


Craig Macmillan  0:15 

So James, you have a interesting company. And you've had an interesting career over the years. But right now, your company does a number of very interesting kind of things in three different areas. And what I was hoping to do is talk about each of those individually in a little bit of detail and have you explain kind of how those things work. First of all, you folks do independent analysis and quality control for grapevine nursery stock production. Tell me more about that.


James Stamp  0:39 

Our clients hire us to find the highest quality grapevine plants for establishing new vineyards. And what we do is to select nurseries that we have previous experience with in terms of delivering good product. And nurseries, where we have previously inspected and tested their increased box and the increase box, as you know, are the rootstock and science sources of materials for propagation. So we, we put together a proposal for our clients to provide the best quality of plant materials that we can. And then we get involved with discussing with nurseries, which materials are best to use. We oversee the testing of those materials, we oversee the harvesting and grafting of those materials. We oversee the production of those materials, that particular nurseries, and we oversee the delivery and final selection of those plants to the vineyard sites. And as part of our, our understanding with our growers, we are available to look at those plants during the course of the vineyard development. We'd like to be there to see how our plants grow. Once they're planted,


Craig Macmillan  1:54 

A grower will come to you and say I'm planting a vineyard, I want to make sure that it's virus free, or disease disease free, I would imagine. And you folks start at the very beginning, you go out and look at the blocks where the first cuttings are going to come from the good gonna go into those plants. Is that right?


James Stamp  2:12 

Yes. When I first started doing this, in 1999, I was asked to look at finished product. In other words, vines that had already been grafted, already been grown in the field, already been growing the greenhouse. And at that point, it's very difficult to have any real control over the quality of the finished product. So it seemed to me like a good idea to start with the source materials that we use to graph the vines and to make sure the source materials, the root stock on the scion, are of high quality and disease, pathogen test negative and that's exactly how we start by finding the source materials for the production of grape vine plants ultimately to be planted in the vineyards.


Craig Macmillan  2:53 

Obviously, if someone's going to plant, let's say hundreds of 1000s of vines, we're talking about hundreds of 1000s of cuttings. Is that right?


James Stamp  3:03 

Hundreds of 1000s of vines. Well, yeah, we're talking a lot of cuttings and in generally speaking from an increased block or rootstock increase block, you might expect to get say 100 cuttings from every mother vine or every increased block vine 100 cuttings for the rootstock. And for the scion material, the Cabernet, the Viognier whatever it might be, you're probably going to get somewhere from 50 buds or 50 cuttings per vine up to maybe 500 cuttings per vine for some very vigorous clones such as maybe Pinot Noir or Cabernet, Sauvignon Blanc we sometimes see 500 cuttings per vine.


Craig Macmillan  3:40 

How many samples are you taking how many pieces of wood are you taking in? What are you testing them for and how?


James Stamp  3:47 

We with the advent or the discovery of Red Blotch, it became clear that the only way to produce vines that are free of Red Blotch disease is to test every plant that is used as a source of materials for that for that finished product. So if you do the math, nurseries will graft anywhere from 1.5 times, one and a half times to two times the amount of vines per finished product. So if you have an order for 10,000 vines, they might refer 20,000 vines. So we have to test enough mother vines or increase block vines which is the correct term, to provide us with 20,000 rootstock cuttings and 20,000, say Cabernet Sauvignon buds. Let's say you've got just for example, a Cab Sauvignon plant that's giving you 500 buds per vine and you want 20,000, you want 20,000 bugs, then you've got to test 40 plants to get 20,000 buds. 40 times 500 is 20,000. Depending on the size of the plant, if its is a large established plant, we want to take more cuttings per vine than if it's a smaller plant, because viruses are not evenly distributed within the mother vine or the increase block vine. So if it's a larger vine, we might take four pieces per vine. If it's a smaller vine we might take two pieces per vine. So that's roughly sort of math that's involved in deciding how many samples we take. We are taking 1000s of pieces of cutting and putting them together into samples that we then test for a range of pathogens. And generally speaking, there are roughly 15 or so, 16 pathogens that fall on our testing list. And they include all the common viruses, the leaf roll viruses, the vitiviruses, A, B, D, Red Blotch virus, Fan Leaf virus, we also test the Pierce's Disease, we also test for Agrobacterium Vits, which is the causative agent of crown gall disease, which is a bacterium. And our pathogen panel depends on really the program that we're involved with. If we're, if we're working with materials where we have a good history of testing, we might adjust the panel slightly. It also depends on the budget, if a client has a limited budget, then we will focus on viruses that we think we'll find or viruses that we have found in the past. So but generally speaking, we have a pathogen panel of roughly 15 to 16 organisms that we look for routinely.


Craig Macmillan  6:27 

And in so it sounds like you're using a composite sample, like you may do a composite sample of rootstock and the comparison sample of scion.


James Stamp  6:34 

Exactly, yes.


Craig Macmillan  6:36 

Does that composite sample comprise a sample from every one of the vines involved?


James Stamp  6:43 



Craig Macmillan  6:44 

So when I get a result back, I can be confident that all the plants that provided the rootstock or the scion are clean.


James Stamp  6:52 

Well, clean is, you know, clean is a word that you will not get anybody, you know, real scientists to use. Okay, these are all virus test negative. It's, you know, it's hard to prove a negative, but the sampling that we do shows that the vines, or the pieces of tissue that we've tested are negative for the virus. And they know and we were sampling for a wide range of pathogens, but it's to say it's clean, to say it's 100% guaranteed not to have viruses. It's something that people don't do because you're it's really, it's really hard to prove a negative. But we've we're sampling, we're sampling every plant and every plant is testing negative. And therefore, we can assume that those plants do not contain the viruses that we're testing for or the pathogens that we're testing for.


Craig Macmillan  7:35 

Excellent. I think that's a really important distinction to make various negative versus cleaning in quotes. So that's the so the points along the way, we've got the rootstock, we've got the scion, is there inspection, testing, investigation as we go through the grafting process and the callusing process and the greenhouse process?


James Stamp  7:53 

Well, really the first, the first step in the process to produce high quality plants is to visually evaluate the scion increase blocks before you test them. So there's no point in spending a lot of money on testing plant materials that don't look good. So we go to the nurseries that we have orders with for the following year, or the year after that. We go to those nurseries and look at their scion increased blocks in October. So we look in October 2021. At the Cab 47, or the Cab 30 or the Sauvignon Blanc 01 or the Pinot Noir, you know 777, and we find contiguous rows and contiguous sets of vines that look healthy. If they look good. In other words, they don't look like the disease, they don't look like they're struggling to grow. Because if a plant is looking diseased, or looking like it's having a hard time growing, that would not be the sort of material you want to select for high quality vine production. So if we see any issues with the vines during our October walkthrough, then we do a couple of things. One, well the nursery is usually with us so the nursery will then want to check those vines and test them or remove them, test them and remove them if necessary, to see if they are virus or there's something else wrong with them. And then once we find clean vines, then we will test them. So the first thing to do is find the clean plants, and this is done in October. Test them. We tag the plants so that we make sure we put our labels on plant materials that we want to graft. And then we see those materials getting harvested and then moved into cold storage and then we're at the nursery when those materials are grafted. So that we can see that the materials we tested and viewed in October and November are now actually on the grafting bench at the nursery February and March of the following year.


Craig Macmillan  9:47 

That's impressive. That is very impressive. Yeah, and I'm assuming you've had good luck with it as it sounds like you couldn't be any more fastidious.


James Stamp  9:55 

You know, it was really an eye opening moment,  I think for me, when Red Blotch became a problem, as you know, it was in late 2012. And we have a lot of plant materials that we were to test for Red Blotch because the new PCR test was made available at that point in time. And it was clear that sampling increased block vines, on a sort of a random basis, sampling the plants in the nursery, the nursery vineyard that gives you the cuttings, not sampling every plant, but sampling say, even I'd say 95% level of confidence with a 5% confidence interval, you're still only sampling a very small amount of plants that are going to be used to give you the cuttings that you need. So the only way to detect the virus, which might only be present in a few plants, but if you're getting 400 cuttings from those one or two plants are infected, you're actually you know, producing a lot of virus that can be contaminated. So the only way to do it is to test every plant.


Craig Macmillan  10:53 

Right. And then is there some additional quality control once they come out of the nursery for you?


James Stamp  10:59 

I mean, nursery production is a very primitive craft, if you will. It's still very, very basic. It's basically putting rootstock and science together and allowing them to graft and providing good conditions for that. And what they want is they want to first of all the cuttings should be have high carbohydrate reserves. So they're strong cuttings. They actually have a good wood to pith ratio. So a small amount of pith, a good amount of wood, which represents good carbohydrate reserves. They should be grown in a way that produces cuttings that are good for grafting rather than growing these cuttings in a way that is good for fruit production. And so we want to see what's going on right from the very beginning. So I actually just gave a presentation the other day. And my first slide on the presentation says that what does every grower want? Every grower wants, or what they really want is no surprises. And that is high quality vines being available, in the right amount, on time and of good quality. Because the last thing a grower wants is to hear from a nursery when they call up and say, you know what, my 10,000 grafted vines delivered in a couple of weeks time and they say, well, we've only got 1000. So what we do, and it's really it's really it really sort of comes with the territory that if you're going to be involved in trying to produce high quality, disease test negative vines, then really in a way, it's I feel like it's on us to make sure the plants exist as well. If you will.


Craig Macmillan  12:22 

So yeah, absolutely.


James Stamp  12:24 

And on the one hand, we you know, we always have this provision that if we do a lot of testing and the plants are diseased at the end of the process, well, then we're not going to plant them. But we do want to make sure that the plants are available for all we can. So we keep we keep very close track on the way these vines are growing after grafting. And so we'd like to see how many plants of the 10,000, that grafted, get grafted, how many get planted up. So maybe in order for 5000 vines 10,000 get grafted, but only 7500 get grafted up. Well, that's actually a good number. But if you graft 10,000 vines, and the only plant 1000 vines up, you know, within four or five weeks of grafting that you've got a problem. And so it's part of our program is to how to solve that problem. So we need to be in touch with the nurseries right, all the time so that if there's a problem, we have time to fix it so that our clients have no surprises. And maybe they have to spend more money perhaps on testing more materials because we found virus, or it may be that the nursery had a bad take, in which case we have to graft more materials. But ultimately, we want to make sure that our clients plant the vines they want on time, and that those vines are of good quality. So what we do is work to solve problems as they develop. And you know, over the years, we haven't had very many problems. But again, I think we paid close attention to what's going on.


Craig Macmillan  13:41 

And suddenly, it just occurred to me, so how many tests per 1000 or 10,000 plants when we're when we're talking about the finished product, how many samples went into, how many tests went into per per 1000, or per 10,000, or whatever?


James Stamp  13:55 

You know, it's very variable. Let's say if you're, we're testing for 15 to 15, or 16 different pathogens, and we may be testing, one set of testing at least two plants for every 100 finished product. So if you've got say 1000 vines then, we're probably testing protesting 20 upfront vines, for every 1000 vines of finished, but actually 20 times, multiply that by two. So 20 rootstock and 20 scion approximately. So we're testing roughly 40 plants for every 1000 finished plants. Those 40 plants are being tested for, say 16 pathogens. So it's 40 times 60. If you do that multiple it's you know, 3200 or something like that, or whatever it is. That's a rough idea.


Craig Macmillan  14:44 

Of actual individual samples, test. I'm gonna pay so much per test, it's going to be 1000s of tests?


James Stamp  14:52 

Yeah, I mean, we test 1000s of samples.


Craig Macmillan  14:55 

I guess. Wow.


James Stamp  14:56 

We have a pretty large business. I think we were probably the The largest business of its kind that does this type of work, I think. Probably anywhere in the world, I guess. And, you know, it involves a lot, it's a lot, it's a lot of work, especially when you're dealing with a biological system like this, which is open to all sorts of climates and you know, biological impact. You know, drought one year can have a, some sort of weird impact the next year. So just like, you know, getting your fruit every year when you're growing your grapevines is difficult, convoluted, it's based on many different parameters. It's the same thing with producing grafted vines. A lot of different parameters affect the look of the finished product. In fact, this year, we looked at a bunch of dormant routings, and they were really super high quality this year did very, very nice, dormant routings this year with just very good internal approach. So not only is the virus testing and the pathogen testing, we've talked about, the other side of what we do is physical quality. We're involved in selecting the best plants that come through the propagation cycle. So for example, if you grafted 10,000 vines, you have an order for 5000 vines, you have 7500 vines that make it through to the finished product line. Well, we want to select the best 5000 of those 7500. And that involves having a good understanding of the parameters that are involved with a grapevine finished product, which include things like does it have a good root system? Does it have a properly healed graft union? Are the wounds on the rootstock shaft properly healed? Do you have good caliper? Do you have good lignification of the shoot spur? And all those, those different facets of the finished product are related to the pathogenic load of the vine when you start off. So if you if you're starting from materials that have high levels of fungal pathogens, and fungal pathogens are everywhere, in the nursery production cycle. And so the way to ensure you have best product is just is to select pathogens that have very good, that have demonstrated very, very good wound healing. Because those vines won't heal their wounds properly, they won't have good graft wounds, they won't have good root systems. They will have rootstock shaft disbudding sites that are not calloused over, they will have lesions running down from the graft union and running up from the base of the plant if they'd been developed or propagated from poor quality plant material. So the physical quality of the vine and vine and the pathogen status of the virus sort of closely interwoven.


Craig Macmillan  17:28 

So this involves looking at every single vine?


James Stamp  17:31 

No, actually it involves, what we do is we we sample every increase block vine that is used to produce the vine. And then we look at the finished product by sampling the finished product in terms of its physical evaluation. And I've been doing this, I mean, I started doing this in 1999. And in 1999, I looked at 1000s and 1000s and 1000s of finished product. And you know, you look at finished product, and you just like anything else, you really get to know what finished product looks like looks like. You get to know, you know what a batch of plants looks like. You know, you get to know how many vines you need to look at, to know in other words, to feel comfortable that you're looking, that what you're looking at is representative of the rest of it. And so you use that information, that experience to help you to determine how to evaluate finished product.


Craig Macmillan  18:19 

And so regarding, actually regarding methodology, it sounds to me like you have a fairly set methodology that you have tested over using years and years. And there's a quantification component to this as well. So you can say we found this percentage of this as opposed to that, as opposed to that.


James Stamp  18:36 

That's exactly right. Yeah. So I think if you would, I mean, you know, things have changed. And we today, we don't get to look at much finished product that we haven't been involved with, right from the very beginning. But sometimes we do and it's always interesting to do that. Because I mean, obviously there's different types of finished product, the potted plants, and then there are dormant bareroot, finish plants. Any any batch of vines that get delivered are going to have some type of defect. The question is, what are those defects and what proportion of the finished product has those defects. So for example, if it's if it's a if it's a severe problem, we'll cancel the order. If it's if it's a severe problem, but in a very small amount of plants, and we know how to identify that problem, then we can have the nursery go back and grade out the bad vines, or we can grade out the bad vines ourselves and take the good vines and get rid of the bad vines. Or we can advise our clients who maybe are buying vines from a nursery I will tell them well this is how you identify the problem in these vines by doing this type of physical manipulation of the plant. It'll tell you what's right or what's wrong with it. But generally speaking, our plants when they've been through our program are very high physical quality with a very small amount of defects or zero defects. Obviously, there's always gonna be some defects. And you really are the final line of defense is the guy who's planting the vine. But our goal is to to sell to our clients vines, the pathogen test negative or very high quality, where there will be no rejects or planting time.


Craig Macmillan  20:07 

So let's move into the field. So you also conducted valuations of newly planted and established vineyards for their performance, presumably in the face of pathogen load. How do you conduct these kinds of evaluations? What kind of methodology do you use?


James Stamp  20:22 

I have to say, I don't do we don't do this, as much as we used to do this was a much bigger part of our portfolio maybe 10, 15 years ago than it is now. And we used to get called out to look at vines, vineyards that have been recently planted. And say, you know, it's a two year old vineyard, and a three year old vineyard. What do we try to do is to, you know, it's important to look at the venue and at the right time of the year. If it's potentially a virus problem, then you want to look at that vineyard in October, when you can see symptoms of virus, they may be well apparent. But the first thing to do is to try and if there's a problem in a vineyard, maybe it's just performing improperly. Is to try and link any visual performance issues with any particular physical attributes that the plant might have, or they may be associated with the site. Simply put, if you've got vines that are growing properly, than those vines that aren't grown properly, have bad graft unions, or have they been planted improperly. And they've got a J rooted root system. I tried to look at the vineyard and say split into say, three into three categories: good vine performance, bad pine vine performance, and say intermediate vine performance. And trying to correlate those different types of wind performance with either a site issue which might be a soil, irrigation, utilization, fungal pathogens, weeds. And then also compare that with just the vine itself. And this oftentimes involves sacrificing vines, but taking, digging that vine up and looking at the root system, looking at the grafting. And it's actually very easy to tell by looking at vines, whether or not the issue that you're seeing is a result of the vine being imperfect at the time of planting, or whether it's more like you know, whether it's related to the way it was planted or where it was planted.


Craig Macmillan  22:09 

That is really, really fascinating. We've kind of run out of our time here, I want to thank you again, James Stamp, Stamp Associates, Viticulture Inc,. There's obviously a lot of work to continue to do. And the work that you folks are doing is wonderful. And I hope that more people will start thinking along the same lines, at the very least I hope the philosophy spreads. Is there one thing you would recommend to our listeners?


James Stamp  22:32 

Yeah, I think what's it's a, it's a big one thing with with sub parts. It really is to pay attention to where your plant materials coming from. To have a really good communication with the nursery. If nothing else, sample the finished finished product for Red Blotch and Leaf Roll Three, which are the two viruses that have the biggest impact on vine performance. And the two viruses that are very easily vectored in the industry.


Craig Macmillan  22:59 

That's great. Where can we find out more about you?


James Stamp  23:02 

We have a website, the website is There's all our, that we have. We've written a bunch of articles about what we do. We give presentations fairly frequently. And so some of that information is on there. And we have a website and of course, phone number, email, of course all that's there.


Craig Macmillan  23:20 

Perfect. Fantastic. Well, I want to thank you again, James, and I want to thank our listeners for listening to Sustainable Winegrowing with the new team. Again, my name is Craig Mcmillan, your host and we look forward to having you download us again.


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