From Mystery Disease to Discovery of Pathogens

"Because the fungi that cause young vine decline can be found almost anywhere, the UC Davis researchers are not recommending that commercial nurseries and the university's own Foundation Plant Materials Service remove healthy plants that carry the fungus." FPMS press release, May 2001.

Phaeomoniella chlamydospora and Cylindrocarpon (black foot fungus) were each cultured from only one of five dormant vines tested. False negatives are common, even in grossly diseased material like this.

More than six years after it was found in California vineyards, "Black Goo"--a name first used by international vineyard consultant Lucie Morton--is no longer a he-said/she said story, but the object of international research and vigorous debate. Mycologists honored Morton recently for "her contribution towards the understanding of black goo [Phaeomoniella] disease of grapevine" by naming a new fungal species after her, Phaeoacremonium Mortoniae. Morton says she does not yet know the viticultural significance of this fungus, which she isolated from a 5C rootstock in 1998.

Professor Doug Gubler of UC Davis is actively researching this problem and others related to what he calls "Young Vine Decline." This term continues to be used to describe a number of diseases caused by several fungal genera (Phaeomoniella, Phaeoacremonium, Cylindrocarpon) affecting vineyard establishment.

Controversy

Growers have blamed nurseries, nurseries have blamed growers, and fungi associated with young vine decline have been found in mother blocks maintained by the University of California's own Foundation Plant Materials Service (FPMS).

The hot button issue still seems to be whether or not the nursery industry and FPMS should be working vigorously to try to minimize the presence of certain organisms in the plants. Should growers be concerned about buying vines with a known-disease agent? Morton and others express concerns about high replant rates, increased susceptibility to environmental stresses, exponential increase in black measles (for which black goo is the precursor), and a decrease in vineyard productivity and longevity.

This vine is five or six years old and has foliar symptoms of measles. It tested positive for phaeomoniealla chlamydospora. "Something happens at the grafting point, says Glenn Friebertshauser of Agri-Analysis in Davis, California. "We often see a dark area of tissue where the scion and the rootstock are joined together."

"We don't know how to get them clean and we don't know if it would help," says FPMS head Deborah Golino.

Golino says that "these types of diseases have not been shown to be controlled effectively by clean stock programs nor has it been demonstrated that the diseases caused by the fungi are spread efficiently in propagating wood."

Gubler advises that the fungi which cause the disease can pretty much be found anywhere in the universe and that growers, first and foremost, should avoid stressing their vines in order to avoid the malady.

According to Morton, "All certification programs are predicated on the fact that growers prefer to start with clean material. Preventing infection in the vineyard is a separate issue." She points to leafroll and fanleaf viruses as examples of diseases that were "everywhere" and which could reinfect clean plants. In spite of this, clean stock programs have dramatically reduced the incidence of these diseases while not eliminating them.

Morton believes that today a number of nurseries and FPMS are aware of the problem and taking steps to deal with it. She is especially optimistic about improved plant material quality and health in the longer term as a result of this awareness. She notes that, "Lionello Petri, the same guy who first wrote about goo, also wrote about fanleaf in 1912. It wasn't until the late 1960s that we really had a good handle on fanleaf. I think the Phaeomoniella problem will be dealt with more quickly because we already have a certification scheme in place."

1995: "Black streaking is normal."

In June 1995, plant pathologists and viticulturists attended a meeting and review of plant materials at Sonoma Grapevines. Attendees included: Andy Walker, assistant professor of viticulture and enology at UC Davis, Doug Gubler, professor of plant pathology at UC Davis, John Mercetich, retired professor of plant pathology at UC Davis, Deborah Golino of the Foundation Plant Materials Service, and others.

Walker's minutes from the meeting say four nursery representatives agreed that streaking was common to nursery materials, and that Mircetich had said all woody grape cuttings exhibit some degree of streaking, and that it could be part of the healing process and not necessarily a disease response.

A letter issued by Sonoma Grapevines after the meeting said the experts "concluded that ‘streaking' was a normal part of the healing process after grafting and that such streaking is not necessarily associated with any disease-causing organism."

"We are doing everything we can to reassure all of our customers, and others in the industry, that there is no substance to the rumor that a fungal infestation exists at Sonoma Grapevines. That statement is simply not true."

Gubler at the time of the meeting confirmed that he had already isolated "acremonium" from declining vineyards, later renamed Phaeoacremonium. He had begun field trials with the same organism the previous year, and they were published in California Agriculture in 1998, demonstrating the pathogenicity of Paeomoniella chlamydospora and cylindrocarpon.

In July of 1995, Lucie Morton organized what would be the first of three seminars in California to place her concerns about black goo within the general context of vineyard replanting and plant material issues. She invited Cornell University grape anatomist Dr. Martin Goffinet to address whether or not black goo/streaking is normal in healthy plant material. After microscopic examination of affected vines, he concluded that it is not normal.

1998: View from UC

In a January 1998 lecture, Gubler said there had not been a single vineyard where the problem had been traced to nursery materials.

Gubler's 1998 California Agriculture article referenced further studies to determine how the pathogens associated with vine decline spread in time and space. It documented many vineyards with problems throughout the state but did not address nursery materials as a source.

	Lionello Petri (1875-1946) Italian plant pathologist who first reported on decline in American rootstocks associated with the black goo symptom and Phaeomonilla, along with other wood discoloration caused by Phaeoacremonium species.

In a paper distributed in Italy the following year, entitled, "Vine decline in California: epidemic or ruse," Gubler wrote that "because of the play it has received in the popular press and by individual consultants it has been blown out of proportion."

(Some have compared these remarks by Gubler on black goo to similar remarks by UC experts on phylloxera. "…due to the overwhelming local and international, out of proportion, typical news media blowup of the phylloxera problem in California. …we continue to recommend AXR1 as a…phylloxera-resistant rootstock" August 6, 1985).

The "Winter 1998" issue of Sonoma Grapevines newsletter Heard it Through the Grapevine reported that Heather Scheck, a post-doctoral scholar working with Gubler, had "sampled all our increase blocks and our dormant cuttings have been declared 'clean.'" It went on to say that Gubler induced young vine decline symptoms in vines by stressing them through either over or under watering. "Bottom line to date is, do not stress young vines."

In March 1999, Scheck and Gubler wrote to Sonoma Grapevines owner Rich Kunde, saying, "we are very concerned about the use of our names and the serious inaccuracies regarding our work at your nursery."

The letter clarified that Scheck visited the nursery in December 1997, collecting nine vines from three lots. "Although no pathogens were isolated from these nine vines, it would be impossible to declare all of your increase blocks 'clean' from this amount of sampling as was stated in your newsletter. Further to our work with dormant cuttings from your nursery, this project is not complete and again we have not declared this plant material to be 'clean.'"

In the October 1999 San Francisco Chronicle article, Sonoma Grapevines owner Rich Kunde "insisted he sent thousands of cuttings to UC Davis and that not one has tested positive for black goo fungi."

In January 2000, Adalat Khan, a post doctoral student under Gubler's supervision and co-author of several vine decline articles from UC Davis, tested cuttings of all of Sonoma Grapevines rootstocks for the presence of Phaeomoniella chlamydospora and Cylindrocarpon. Three cuttings of each of their 21 rootstocks were tested and all 63 cultures were reported as negative.

These UC Davis results were then posted on the Sonoma Grapevines website and used in their advertising. An ad in Wine Country Classifieds: said it all: " Taboo Subject . . . . . young vine decline. We have been testing for it since tests were developed. Check out our website for the latest Uit was settled in 2001.

Figure 1. Dondero Test Results

2001	California Grapevine	101-14	Rootstock	Phaeomoniella Chlamydospora 1/5 Cylindrocarpon 1/5
2001	California Grapevine (Sunridge)	3309	Rootstock	Phaeomoniella Chlamydospora 1/5
2001	California Grapevine	4453	Rootstock	Phaeomoniella Chlamydospora 2/5
1999	Vinifera	101-14	Rootstock	Phaeoacremonium spp. 2/2 Cylindrocarpon 2/2
2000	Vinifera	101-14	Cabernet Sauvignon	Phaeomoniella Chlamydospora 2/10
2000	Vinifera	4453	Cabernet Sauvignon	Phaeomoniella Chlamydospora 3/10
2001	Vinifera (Vintage)	101-14	Rootstock	Negative
2001	Vinifera (Vintage)	5C	Rootstock	Phaeomoniella Chlamydospora 5/5
1999	Sonoma Grapevines	101-14	Pinot Noir C115	Phaeomoniella Chlamydospora 2/7 Cylindrocarpon 3/7
1999	Sonoma Grapevines	101-14	Pinot Noir C777	Phaeomoniella Chlamydospora 3/7 Cylindrocarpon 5/7
1999	Sonoma Grapevines	3309	Pinot Noir C115	Phaeomoniella Chlamydospora 3/9 Cylindrocarpon 5/9
1999	Sonoma Grapevines	3309	Pinot Noir C777	Phaeomoniella Chlamydospora 1/5 Cylindrocarpon 1/5
1999	Sonoma Grapevines	5C	Chardonnay D35	Cylindrocarpon 1/4
1999	Sonoma Grapevines	1616	Pinot Noir	Phaeomoniella Chlamydospora 2/5 Cylindrocarpon 1/5
1999	Sonoma Grapevines	4453	Sangiovese	Phaeomoniella Chlamydospora 1/5 Cylindrocarpon 1/5
2001	Borri	5C	Rootstock	Phaeomoniella Chlamydospora 5/5
2001	Duarte	Ripria Gloire	Pinot Noir	Phaeomoniella Chlamydospora 2/5
2001	Duarte	4453	Pinot Noir	Negative
2001	Duarte	St George	Zinfandel	Phaeomoniella Chlamydospora 1/5
2001	Duarte	3309	Syrah	Phaeomoniella Chlamydospora 1/5
2001	Herrick	101-14	Rootstock	Phaeomoniella Chlamydospora 1/5 Cylindrocarpon 2/5
2001	Martinez	101-14	Rootstock	Negative
2001	Martinez	3309	Rootstock	Negative
2001	Martinez	4453	Rootstock	Phaeomoniella Chlamydospora 2/5
2001	Galo Maclean	S04	Rootstock	Phaeomoniella Chlamydospora 3/5 Cylindrocarpon 1/5
2001	Galo Maclean	101-14	Rootstock	Phaeomoniella Chlamydospora 1/5 Cylindrocarpon 1/5
2001	Galo Maclean	3309	Rootstock	Phaeomoniella Chlamydospora 1/5 Cylindrocarpon 1/5

Dondero's test results from the past three years, demonstrating widespread infection in dormant nursery materials (2001 lots from vinifera originated at Vintage and were "brokered" by Chris Lindelof of Grey Creek Viticultural Services, formerly of Sonoma Grapevines). One California Grapevine lot was delivered with Sunridge tags. Duarte vines were one-year old potted vines. Tests were conducted by Forensic Analytical of Rancho Dominguez, California.

It was in the midst of Dondero's litigation while Gubler was serving as an expert consultant to Sonoma Grapevines that Sonoma Grapevines published the UC Davis results declaring their rootstocks free of vine delcine pathogens.

"When I first found I had planted disease in the Spring of 1999, it only took me a few months to appreciate that the disease was widespread in the county, that nurseries were actively shipping vast quantities of infected material, and that vineyard failures due to decline pathogens were blamed on anything but the disease present in the vines at the time they were planted," says Dondero. "Within a few weeks, I knew of at least a dozen failing vineyards. Some came from patients, others from industry contacts. It took me about a year to firmly conclude that UCD was complicit just as much as the nursery industry."

With additional acreage to plant, Dondero has now tested the production of eight nurseries encompassing 27 nursery lots. Eighty-five percent of them were positive for one or more of the fungi associated with vine decline (see Figure 1). He adds that one or two of the others appear infected on cross sections and are probably false negatives. He has also tested a dozen lots with a newly developed PCR test. He finds the PCR test unreliable and recommends that growers not rely on the results in seeking out clean material.

"Taken at face value, any of the publications or statements from UCD may be plausible," says Dondero. "It is the pattern of inconsistencies, nursery defense, and denial taken together with extreme variance from researchers elsewhere on the globe that makes a compelling argument that UCD is covering up this mess."

Dondero points to the following:

• The AxR-1 debacle. "UCD has never come out and said they erred but there is a widespread consensus that they blew it big time and compounded their error by inventing ‘phylloxera biotype B,'" he says.

• FPMS. "Several times Golino and Gubler have referred to vines at the foundation vineyards that have esca symptoms. There is every reason to think that FPMS is shipping phaeomoniella-infected material just like the rest of the nursery industry," Dondero says.

• FPMS fees. "Every certified rooting and bud generates a small fee that is paid by growers and passed along to FPMS," says Dondero. "The widespread perception that infected certified material is likely to lead to poor long term results might result in a significant drop in vineyard plantings and a substantial decrease in revenues to FPMS, as well as undermining the entire system of certification."

"In 1995, UCD was quick to come to the aid of the nursery industry and quell the 'unfounded rumor' about a disease present in nursery stock. There was no problem we were assured. By 1998, Phaeomoniella and Cylindrocarpon were clearly identified as pathogens causing vine decline in vineyards throughout the state. But it wasn't coming from the nursery. Now in 2001, we hear thatit is in everything (almost) but it doesn't make any difference. They need to get their story straight."

Black goo is a "dirty little secret," says St. Francis Winery CEO Joe Martin. "There are a number of growers that will be losing their vineyards if they're not careful, and the lending institutions I would think by now would wise up and say 'bring in your order for rootstock to us,' to assure the guys won't make mistakes."

"Of all the stuff we have done wrong that has happened, why would we somehow try to put this one under the cover?" asks UC Davis department of viticulture and enology chair James Wolpert. "If we make a mistake we say so."

Delivered by Nurseries or the Wind?

In February 2001, Gubler spoke at a large gathering of growers in Sonoma held to discuss the issue. "We think this is mainly coming in on airborne spores and pruning wounds," he advised. "We don't think much of it is coming from the nursery."

In the May/June 2001 issue of Practical Vineyard and Winery, consultant Mike Porter reviews much of the recent international research. The article, a toned down version of Porter's views, questions the hypothesis that stress causes the malady. It describes goo as an old European species in a new American host (rootstocks), just as phylloxera was an old American species in a new European host.

Porter's presentation included extensive results from 1995-1998 demonstrating infection in a majority of pre-plant rootstock and dormant vines. His results parallel Dondero's results though he discretely omitted the sources of his material. Most of Porter's cultures were done in Gubler's lab.

In May 2001, the story from UC Davis and FPMS changed as they issued a news release saying, "It may not be possible to produce vines that don't have these fungi, which have the ability to survive both in the soil and plant tissue and can invade the plant in so many ways."

Attached to the release was a fact sheet advising growers to "eliminate the environmental stresses that seem to cause the disease."

"We were well on our way to this being a 'disease' in California," says Porter, "and then word got out that the foundation vineyard is infected. Then suddenly it was declared not a disease--that's when it became 'stress.' That was two or three years ago. The new tact is to blame it on stress, the same thing they did with AxR-1."

"What I have seen, time after time, is 'nursery a' is good, 'nursery b' is bad," says Julian Whaley, who for two decades was professor of plant pathology at California State University, Fresno, and now runs an independent plant pathology consulting service.

"It is very, very clear that some nurseries have been producing very high percentages of infected plants," says Whaley. "It is obvious that this comes from the nursery."

"Whenever you come in and start a new vineyard and 'nursery a' is all diseased and you plant them right along side vines from 'nursery b' and there is no disease, that eliminates the problem in the soil."

"The Italians have recognized that this disease comes from nursery stock long bfrom phaeo," says Duarte "And they're ready to go to a new generation mother block over the next couple years. They won't be available in the near-term. We have that effort underway just as a general stock improvement program as a nursery. But this year, with the same mother blocks we've been producing vines with for the last 13 years, we've had the best quality we ever had, just due to good practices, general sanitation and coaching."

"Even if you're perfectly clean to start," says Duarte, "re-infection is possible."

Duarte says five or six factors likely determine whether a vineyard will have a problem but "the least variable is whether the mother block that the cuttings come out of have Phaeacrimonium and Cylindrocarpon."

"What hasn't been talked about is, if it's vineyard practices, what are the performance standards for good quality nursery stock?"

"What questions should a grower be able to answer with some specificity in terms of how the vines are cared for?" asks Duarte. "There are some basic questions most growers should be able to answer in establishing a vineyard."

"Consultants say it's the nursery stock but there's no mother-block in the world that can claim to be free of it."

"We know the agents and that it's a fungal disease, but it appears these fungi that cause the disease are pretty much in every piece of wood you can test," says Ernie Bowman of the Kendall-Jackson Nursery. "There appears to be some type of chemical agents you can use to clean the wood, but according to current research, these fungi have lived in grapevines for hundreds of years."

"The fungus is like a parasite, it doesn't typically kill the host plant. But something now is causing that relationship to break down and the fugus is parasitic on the vine."

"If the assumption is this fungus can be in any piece of wood because it is in the ground and in the air, it is very widespread. It would be great if we could get it out, but I'm not sure if that's practical given the way it seems to exist in the world we live in. I'd love to be able to get rid of this fungus. Can we do that?"

These organisms have been around from day one," Sonoma Grapevines owner Rich Kunde says. "The difference is we have doctors and lawyers planting vineyards today and all kinds of new rootstocks and some of these are not as forgiving as say AxR-1--where they really love water."

Kunde, certainly not the only nursery to have large orders rejected in recent years by growers, says he was singled out.

"I think Dr. Gubler has pinpointed the fact that it's all involved with stress. People can scoff at it, but let me tell you, dealing with thousands of growers, there's a lot of difference in the way people grow vines."

"It is unfair to say it's a nursery's problem when it's a management problem. The grower's accepted the vines and thought they were beautiful. Can the nursery be responsible three, four and five years after the fact?"

Stress: The Chicken or The Egg

"Telling growers things like--don't stress young vines, don't crop them for 3-4 years and be sure the roots point down--is good generic advice," says Morton. "No grower today is going to intentionally stress their plants to the point that they don't grow. However, from day one, I've been emphasizing that goo must be seen in the larger context of plant material quality, site preparation, and young plant care. In the absence of a sure source of clean material, the obvious recommendation is to stimulate young vine growth as much as possible because goo clogs conductive tissue and reduces stress tolerance."

Morton continues, "This is a slow-growing fungus that does seem to proliferate faster where it comes into contact with a greater proportion of dead wood such as occurs in older vines with accumulated pruning wounds or poor quality bench grafts with deep disbud scars and semi-necrotic graft unions. Ironically, the first few goo vineyards that caught my attention grew like gangbusters for the first four years and then started to have unexplained spur dieback. I'm afraid that growers who planted in the mid-1990s and have yet to recognize this problem will discover this in the coming years."

Porter says nurseries "love the assertions that the disease is all about stress."

"If you have a dying vineyard, they come and try to find something wrong. What vineyard is perfect? You can always find something wrong but the smokescreen has been annoying because it's all speculation."

"You have dying vines and they say, ‘maybe you didn't irrigate enough'. ‘Oh you did irrigate? Oh well you must of irrigated too much.' I've heard every excuse except ‘radiation damage from Elvis' UFO,'" Porter says. "They speculate that you did something wrong and walk away."

"Not all nurseries do that," says Porter, but he cites instances where nurseries tried to resell large orders of rejected material.

"These can be very slow pathogens, you can find apparently healthy vines that are infected, so it must not be a disease," Porter quips.

"A lot of growers have tuned out the University on this issue," concludes Porter. "I predicted years ago that the marketplace would act before the government would. The industry has spoken with their dollars. You've seen big changes in the nursery business."

Porter allows that the fungus is all over, and notes that the Romans described it in their vines. "They're saying it's only a problem if you stress the vines. That's exactly what they said about AxR-1 and phylloxera. If you don't stress the vines, they'll be OK. It turned out to be wrong."

Gubler Focuses on Pruning Wounds

"This thing is very confusing. I wish it was just one fungus doing the damage," Gubler says. "It would have been figured out a long time ago."

"We now know that these fungi are ubiquitous in grapevine production regions and if you plant a clean plant in a vineyard, the likelihood of it staying clean from this fungi is probably about one in ten million."

"There has been a lot of mud slinging out there by mostly a few individuals," he says. "Basically, people were talking without knowing what the hell they were talking about. We were hesitant to say much (at first) because we weren't sure what we were dealing with."

"There is no doubt that some of this stuff is coming out of the nurseries, but not to the extent people have been claiming."

The nurseries are very concerned," says Gubler, who also reports that he is speaking with them about a potential new project looking at plant production and potential sources for contamination.

"We have looked at the mother blocks, and there are in fact some vines out there that have the fungi," says Gubler. "But it is a ‘big leap' to assume that because the fungus is there, that the daughter plants will have the fungus in them."

"We know that these organisms are in every vineyard in the world, and they were first identified in 1901, so what does that tell you? "

"I've been trying for five years to quash this thing," Gubler says. "It is frustrating when you are dealing with zealots. Unfortunately, there are people out there listening. The whole thing has been blown out of proportion."

Gubler says UC Davis will soon recommend growers treat their pruning wounds to stop penetration of fungi through pruning wounds. Gubler, who has been able to show that Pc produces spores that are successful in attacking pruning wounds up to four months old--is engaged in a plethora of interesting research.

"We know that in the pruning wound studies, paints used for eutypa control will giveus excellent control of these organisms," Gubler says "We have a new pruning wound treatment."

"We want to get a couple of chemicals registered for nurseries to use that would help in cleaning things up," says Gubler. "By cleaning things up, I mean surface sterilizing the plants. One nursery built a vacuum infiltration chamber, where they put their cutting in this chamber in a liquid bath of some fungicide."

"We just lost the fungicide Benlate as a control for eutypa," says Gubler. "We've got a new one that should protect for the four-month period that the wounds are successful. We've got it registered, and it is in the pipeline. We were just going to release it to the growers but no chemical company would pick it up unless it had a patent on it. We're patenting it through the university, and that's where it is right now."

"We feel like we're gaining some knowledge in biology and epidemiology," offers Gubler. "We know that Pc produces structures that allow it over winter to survive from year to year. It's a major find. It tells us a lot about the organism.

"We've also been able to show conclusively that all of these fungi will grow in every part of the grapevine tissue. The spores will germinate directly and penetrate through the epidermis of roots, leaves, pedals, shoots, and fruit."

On the issue of pruning wounds, Morton says that for Phaeomoniella in rootstocks, which are not pruned after grafting anyway, this is closing the barn door after the horse is out. "When vines arrive with an endophytic fungus already present, what good does it do to paint the pruning wounds? Australian researchers point to wounds as points of egress for Phaeomoniella--exit points from internal infections." Morton adds that, "This is not to say that wounds are not entry points for fungal spores. After all, the grafting process involves the joining of two "wounds" and research shows that scrupulous sanitation during the propagation process does lead to a significant decrease in the number of plants testing positive for Phaeomoniella."

Inspecting Mother Blocks

"You can't go to one vineyard anywhere in the world and not pick the fungi up, so it's ridiculous that they made this jump between black discoloration in the vines at FPMS--and saying that therefore everything in the world came from there," says Gubler. "That's just not true."

"Nobody ever looked at rootstock mother vines," says Morton. She points out that around the world--not just in the US--many of the new rootstock blocks of the last 25 years came from a small number of mother vines due to the use of virus-tested foundation sources.

"A few infected certified rootstock mother vines blown up to meet the demands of the AxR-1 crisis are a plausible explanation for how an unknown problem could become widely spread. However, it is not true that every vine is infected. I've seen clean vines, but rarely have a way to know their true origins. It would be great if UC Extension would do a thorough survey of this."

A recent rootstock susceptibility study conducted by Gubler shows that AxR-1 is highly resistant to the fungi. "Infection can occur but there isn't much going on when it gets there," says Gubler. "All of the new most popular rootstocks, 3309, 1120R, 5C, 101-14--just to name a few--show a pretty good level of susceptibility. What we are dealing with here is the fact we are using new rootstocks that are more susceptible to these fungi. Obviously we're going to see new problems."

And if the results of Porter, Dondero and others is to be believed, a lot of acreage has been planted with infected matieral.

Morton agrees that genotype will turn out to play a role in this. "The fungus seems to behave differently in the European [Vitis] vinifera species than in American species such as V. riparia." The xylem vessels, where the goo fungus lives, are larger in American species than in V. vinifera according to Morton.

Foundation Plant Materials Service at UCD

FPMS head Deborah Golino acknowledges that concerns have been raised about the possible transmission of young vine decline fungi and the fungi associated with the disease syndrome known as "esca" in Europe in wood sold by FPMS to nurseries. "Although I know of no evidence that this is true or even possible, I am doing everything I know how to reduce any chance of moving disease with our plant materials."

Golino notes that she has been in close communication with plant pathologists around the world. "My participation on the Plant Pathology committee of the OIV (Organization International de Vigne et du Vin) and the ICVG (International Committee for the study of Virus and Virus-like Disease of Grapevines) have provided me with good opportunities for discussions with the global community of researchers in this area. Further, the Annual International Workshops on Grapevine Trunk Diseases (see James Stamp article) has made it easy obtain the latest information on these issues in excellent detail. I think any careful reading of the literature in this field would bring a thoughtful reader to the same conclusion: we do not know how to control young vine decline and most treatments are either experimental or controversial. However, there does seem to be a connection between good vine health, low vine stress, and freedom from the young vine diseases."

"FPMS has a number of prophylactic procedures and treatments which may reduce the possibility of transmission of pathogens with our cuttings. Although there is little evidence that one-year old cuttings can spread young vine decline disease (the form in which most FPMS grape stock reaches nurseries and growers), we felt these procedures could not be harmful and might be useful. Many of them have been in use at FPMS for years in our general effort to improve vine health.

"Foundation vines are inspected multiple times throughout the season by Dr. Adib Rowhani, FPMS Plant Pathology Specialist, and twice a year by a team of CDFA biologists, UC and USDA scientists, and County Agricultural Commission staff. Vines which show signs of eutypa, measles, or "esca" are put on hold. Our oldest collections are being replaced by younger vines to reduce the incidence of these "old vine" diseases in the collection.

"Vines are sprayed with a copper based fungicide just before leaf fall to reduce any microbial populations on the surface of cuttings before they are harvested. A dormant spray is also applied to the vineyard before bud break. All pruning wounds are treated with fungicide to reduce the possibility of infection by wind borne spores. During the growing season, in additional to sulfur treatments to control mildew, several applications are made of systemic fungicides which are known to have broad based activity against grapepathogens, even within the vascular system.

"One new FPMS program that might be of interest is our Next Generation program. Aware that decades are often required to implement new technology and create new Foundation planting (therapy, testing, planting, and professional verification of new vines often each take years), we have proposed and received funding from the IAB (Fruit and Nut Tree and Grapevine Improvement Advisory Board). We are creating a new collection of the major grape varieties and rootstocks which have been propagated through microshoot tip culture, which is known to eliminate viral, fungal, and bacterial diseases. They will be screened using the latest PCR DNA detection technology, as well as traditional tests, for all known grapevine viruses (including minor and new viruses) as well as crown gall bacterium. We see this as the next step in improving our Foundation grape collection."

"When the epidemiology of young vine decline becomes better understood, we hope that effective control techniques will result from our increased knowledge," says Golino. "If it is discovered that these control techniques can be used in the Foundation vineyard, they will be implemented immediately."   wbm   

Selected Resources:

Black Goo, Symptoms and Occurrence of Grape Declines, edited by Lucie Morton, 1999, International Ampelographic Society

Phytopathologica Mediterrania, Special Issue on Esca and Gravevine Declines, 2000, Mediterranean Phytopathological Union

Mystery Diseases Hit Young Vines, Wines and Vines, November 1995.

Update on Black Goo, Wines and Vines January 1997

Grapevine Decline in California, Practical Winery and Vineyard, May/June 1998

International Perspective on Young Vine Decline, Practical Winery and Vineyard, May/June 2001.

Grapevine Nursery Developments, Wine Business Monthly, February 2000

On the Internet: The UC Davis Plant Pathology Department website on Young Vine Decline is located at http://yvd.ucdavis.edu/default.html