|Many thousands of young vines
in vineyards in the North Coast of California have performed poorly
over the past decade. Discussions of this problem with pathologists
from around the world indicate that, although much research remains
to be done and opinions differ on a number of details, a consensus
has recently emerged regarding the nature of the beast.
It has been difficult for many people to accept that young vine decline
is a serious problem. This is understandable, following as closely
as it does on the heels of the AXR-1 debacle. But there is a worldwide
disease problem. In fact, it is a complex of different fungal diseases
infecting American rootstocks, including Phaeoacremonium, Cylindrocarpon,
and especially Phaeomoniella.
As noted by viticultural consultant, Dr. Richard Smart, Most
growers and professionals enter into denial, which is to be expected.
Anyone unfamiliar with this attitude should read George Ordishs
account of the phylloxera invasion of Europe to see the close parallel
that existed about 100 years ago.(1)
The fungal diseases mentioned above are often present in rootstocks
at the time they are delivered from the nursery. It is highly undesirable
to plant these diseased vines. Dont be surprised if vines that
should have been rejected do poorly or eventually die.
Sonoma County vineyard owner, Brian Gebhart recalls that, in the 1970s
planting boom, demand outstripped supply, and a lot of inferior plant
material was delivered to growers. The high loss rates experienced
in the 1970s should serve as a lesson today. Growers should be very
picky in culling out poor plant material.
Table I shows rootstock, while Table
II shows dormant bench grafts picked up on planting day in North
Coast vineyards and sent directly to pathology labs at UC Davis and
California Department of Food & Agriculture from 1995 through
1998. Please note that some of what was called Phaeoacremonium a few
years ago has been renamed Phaeomoniella, and that these two different
fungi were not distinguished at the time.
During the same period, samples were taken from existing vineyards
having a great many sick and dying vines. A total of 31 vineyards
representing eight rootstock genotypes from five different sources
were pervasively infected with Phaeomoniella, Phaeoacremonium, Cydlindrocarpon,
and a smattering of other fungi.
While studying grapevine decline in Portugal,
Dr. Cecelia Rego et al tested 3,340 unplanted vines representing
nine different rootstock genotypes.(2) They
found that 30% were infected with Cylindrocarpon and 23% infected
with Phaeomoniella. (The infection rates of Phaeomoniella are likely
understated; see false negative under More confusion
Rootstock mother vines are widely infected with some of the same
fungi listed in Tables I and II. Specifically, Phaeomoniella, Phaeoacremonium,
Cylindrocarpon, and Fusarium have been found in rootstock mother
vines and their offspring in California, Europe, South Africa, and
New Zealand. Dr. Ian Pascoe reported extensive Phaeomoniella infection
of rootstock mother vines and stunting, decline and dieback of vines
one to 24 years old in Australia.(1)
There may be no apparent foliar symptoms in rootstock mother vines
look inside to detect damage. But in vines grafted onto young rootstocks
of American parentage, these fungi can be serious pathogens with
a wide range of symptoms.
Infection of harvested canes can be both internal and external.
That is, some canes have spores in their xylem vessels and pith
which remain essentially dormant as long as the tissue is green.
After propagation and one year in a nursery plot, the pith and first
xylem ring are woody enough for the spores to germinate (personal
communication from Dr. Laura Mugnai). More canes (likely many more)
have abundant spores on the outside, which get in during propagation
through a disbudding site or via one of the end cuts.
Note in Tables I and II
that some of the fungi, specifically Cylindrocarpon, Fusarium,
Pythium, and Botryodiplodia, are known to live in soil and would
more easily be kept out of the vines if the canes were not allowed
to drape onto the soil. To prevent this problem, rootstock mother
vines should be trellised and shoot positioned, and harvested canes
should never come in contact with the soil. In contrast, scientists
have not found that Phaeomoniella infection can be transmitted through
soil or that treating the soil is curative for esca or young vine
The presence of abundant spores of the various pathogenic fungi
should be of great concern to both nursery staff and growers. During
the process of grapevine production, each rootstock is wounded at
both ends when it is removed from the mother vine, disbudded at
two sites, and injured during grafting.(2)
It is important to note that Pch (Phaeomoniella) produces
pycnidia on the surface of grape wood, says Dr. Doug Gubler,
UC Davis Department of Plant Pathology. The conidia produced
from these pycnidia infect rootstock through the cut end and wounds
produced by disbudding.(2)
Disinfection of the canes prior to cutting and propagating could
prevent a great deal of disease. Unfortunately, only a few nurseries
in California do this effectively.
Some California nurseries wash the cuttings and often soak
them in tanks with diluted chlorine (followed by clean water rinse)
before cold storage, reports Dr. Andrew Walker, UC Davis Department
of Viticulture & Enology. Cuttings are rehydrated before
grafting and a disinfecting dip in chlorine, and occasionally Benlate,
is used to control fungi.
In an Italian experiment
reported at a New Zealand seminar last year, Dr. Laura Mugnai compared
sterile and conventional propagation of cuttings from
rootstock mother vines that were known to be infected with Phaeomoniella.
Sterile propagation consisted of soaking the canes in clean water
and ENOVIT fungicide, (which is 70% tiophanate-methyl at a rate
of 1% by weight) keeping all tools sterilized, and growing the vines
in a greenhouse in sterile planting media. Of the conventionally
propagated vines, 49% ended up infected, compared to only 15% of
the sterile propagated vines. (These statistics likely understate
infection rates, see false negative under More
This experiment may give a good indication of rates of internal
versus external contamination. Dr. Mugnai also notes, Isolation
experiments carried out on more unplanted bench grafts of different
scion/rootstock combinations from nurseries in both Italy and France,
fully confirmed these results.(1) The same
wood browning was present in almost all the samples and P. chlamydosporum
[now called Phaeomoniella chlamydospora] was isolated from 22% of
them. (Very similar to Dr. Regos result.)
In 1994, Dr. Strauss Ferreira published results of experiments
with Phaeomoniella (then called Phialopora parasitica), which showed
that the fungus gives off toxins which strongly inhibit callus formation.(3)
In Dr. Gublers trials, it was found that, in cuttings exposed
to inoculum, callus formation was partially to completely inhibited.
Infection not only affected callus formation, it also reduced plant
height, number of internodes, number of roots, root length, and
dry weight above ground.(2)
Poor callus formation, root growth, and top growth are all red flags
for growers, indicating either infection or poor callusing conditions.
Regardless of cause, poor growth and callus formation are undesirable
In hot water
Much research has been done, especially in Australia, using hot
water to improve viability and reduce pest and disease problems
in dormant plant material.(1) It is highly
unlikely that such treatment will eliminate all young-vine-decline
pathogens; results to date are encouraging enough to merit continued
Regarding callus formation, hot water treatment of dormant rootstock
cuttings prior to propagation is most encouraging, according to
Helen Waite and Peter May, Institute of Land and Food Resources,
University of Melbourne, Australia.(1) If the
process also reduces or kills pathogens, so much the better.
to planting day
Given the discussion above, growers should thoroughly inspect each
vine before accepting or rejecting it. The root base, disbudding sites,
and graft union should all be completely callused. Anything less than
100% callus of all propagation cuts is cause for concern and likely
rejection. Roots should be evenly distributed around the root base
with no sizable gaps. Flat sides connecting disbudding sites or stem
grooving should also be rejected.
One option to avoid these fungal diseases is to plant rootstock for
field grafting. Inspect each vine one-half hour to one hour after
the top is cut off. Any sap bleeding from the cut should be clear,
not brown or black. Get some of the vines showing symptoms tested
in a pathology lab. If any of the vines test positive for Phaeomoniella
or Phaeoacremonium, growers should seriously consider pulling out
all vines with symptoms.
If only Cylindrocarpon is detected and your soil is well-drained,
it may be desirable to wait and watch the growth, since vines have
been known to outgrow this particular fungus in a few years if the
soil is not excessively wet. Over-irrigation of Cylindrocarpon is
generally thought to be a bad idea, while some feel that under-irrigation
of the Phaeos is likewise a mistake. If you have both in your vineyard
and cannot tell them apart visually, how will you make irrigation
decisions? You are much better off not planting diseased vines.
|Regardless of the type of vines that you
are planting, you should discuss these diseases and the nurserys
policy toward these diseases in advance of placing your order. Read
the contract carefully, especially the warranty regarding disease
Prior to taking delivery, it is wise to go to the nursery plot containing
your vines and randomly dig some of them up. Any vines showing callusing
problems should be tested in a pathology lab, and you should be prepared
to do some slicing and dicing in the field and closely examine the
xylem with a hand lens. Cutting into rootstock mother vines can also
Normal functional xylem does not have tar-like contents inside
the vessels, nor dark amber senescent cells surrounding those vessels,
notes Dr. Martin Goffinet, Cornell University grapevine anatomist.
Living functional cells in fresh tissue are creamy greenish
in young tissue near the cambium or creamy beige in older wood near
the pith. In terms of a pathogen-free vine, the presence of black
goo is not normal. Black material that is isolated in vessel
elements is not a normal occurrence, even in very old xylem tissue
formation. Goffinets guided tour (with photos) of the
grapevine vascular system is highly recommended reading.(1)
Keep in mind that these diseases have been under-reported on Californias
North Coast. This is understandable in light of the tremendous expenses
incurred in the AXR-1 debacle. Many growers simply do not wish to
think about widespread infection of their new vines, and they certainly
do not want to scare their bank, investors, or partners.
But it is vital that growers talk to each other and to the nurseries,
so these diseases get cleaned up. Research is slow and state regulation
of nursery practices takes even longer. It is up to growers to motivate
nurseries to be proactive. Land prices and development costs are far
too high for continued complacency.
One hopes that certification will some day include fungal pathogens
along with virus, but that is not likely soon. Technical hurdles appear
challenging and the political barriers even more so.
Where did these pathogens come from? Actually, they have been here
all along as esca (known in California as black measles),
which the Romans described in their vines according to Giuseppe Surico.(2)
The difference is that esca involves Phaeomoniella and other fungi
in the European vine Vitis vinifera above the graft union and mostly
Phaeomoniella in the American rootstock below the union.
Young vine decline involves infection with Phaeoacremonium, Cylindrocarpon,
Phaeomoniella, and possibly some others in American rootstocks below
the graft union. Esca infects pruning wounds and gives off spores
from pruning wounds above the graft union on Vitis vinifera when it
Young vine decline is essentially a group of diseases in rootstock
mother vines, inadvertently propagated at the nursery. The European
fungus Phaeomoniella and European vine Vitis vinifera have lived together
for thousands of years and have been subject to human selection (see
Charles Darwins work on human selection of domestic species
for a better understanding of how the vine and a fungus could get
along). On the other hand, European fungi and American rootstocks
have had only had one century to get to know one another, too short
a time for even artificial selection to have done much.
What we now call Petris vine decline was first reported in 1912
in Italy by Dr. Lionello Petri, who found the Phaeos in declining
vines up to 18 years old on four different rootstocks, including AXR-1.
He went on to study a number of diseases now known to be caused by
Interest in Phaeomoniella re-surfaced in the 1950s when Dr. Luigi
Chiarappa studied black measles (esca) in California and
Europe, but his efforts were set aside when he went on to study other
crops. In the late 1980s, Dr. Phillipe Larignon, Dr. Bernadette Dubos,
and others in Europe rekindled study of this pathogen in relation
to esca, while Dr. Strauss Ferriera was working with the same nasty
fungus in association with slow dieback of vines in South
Apples and oranges
Although studies of esca and young vine decline currently overlap,
the results in one area are not necessarily applicable to the other.
For example, some studies relating to young vine decline have used
Vitis vinifera instead of American rootstocks. Given that various
genotypes of European and American vine species are unlikely to
respond in the same way to various pathogens, it is very likely
best that American rootstocks be used in research pertaining to
young vine decline and Vitis vinifera be used when studying esca.
Dr. Larignon found internal infection of Phaeomoniella in Vitis
vinifera canes only about 1% of the time while studying esca.(2)
In Dr. Mugnais work with American rootstocks, the internal
infection rate was much higher (see Italian
experiment under At the nursery
above). It is worth noting that a study of esca and eutypa published
in 1992, Dr. Larignon et al found Phaeomoniella in 40% of samples
taken from American rootstocks, Phaeoacremonium in 5%, and Sphaeropsis
in less than 5% with a more diverse mixture of fungi from the graft
union up (1).
A rose by any other name
Some confusion has arisen because of name changes. Here is the latest:
1) What Dr. Petri and Dr. Chiarappa called Cephalosporium and
Dr. Ferriera called Phialophora is Phaeomoniella, and it causes
Petris vine decline (also known as slow
dieback and black goo).
2) What Dr. Petri called Acremonium is now Phaoeacremonium,
which along with Phaeomoniella, Cylindrocarpon, and possibly a few
other fungi, causes young vine decline (an umbrella
term often used in California).
3) Two species of Phaeoacremonium, angustius (CBS 249.95) and
inflatipes (CBS 222.95), both found in vines in California, are
being recommended for reclassification as the much more common Phaeoacremonium
aleophilum. What was commonly reported as inflatipes in California
Adding to the confusion, the type of culture testing currently practiced
to detect the fungi responsible for young vine decline is subject
to false negative results. That is, the fungi can be
present yet not be detected. Estimates vary, but 60% detection and
40% false negative from 100% infected wood may be about right for
Phaeomoniella, according to Glenn Friebertshauser, Agri-Analysis.
That is, if a vine is infected, there is only a 60% chance of detecting
the infection via culture.
This helps us to understand how vines that show the long,
dark brown striations, that can reach all the way to the roots
that Dr. Petri described can test negative. Or, as Dr. Pascoe says,
It appears that the goo may be produced at some
distance from the infected cells, and this suggests that a toxin
may be involved and also explains why were sometimes unable
to isolate P. chlamydosporum from perfectly typical symptoms.
Please review Tables I and
II again with the understanding that a bit more than half of
the actual infections of Phaeomoniella were likely detected.
If all of the vines that you send in for testing have internal and/or
external symptoms associated with fungal infection and some test
positive while others test negative, it is likely that all are infected.
False negatives are a nagging problem not just in viticulture, but
in human diseases as well. As they say, Absence of evidence
is not evidence of absence. When in doubt, get more vines
It is common for vines showing no foliar symptoms to have internal
symptoms in the rootstock xylem and to test positive. Some have
interpreted this to mean that the fungi involved are either weak
pathogens or not pathogens at all. Please note that apparently
healthy people are infected with HIV and hepatitis C
a slow pathogen is not necessarily a weak one.
On the North Coast, we are seeing the onset of decline in vines
anywhere from one to 12 years old. Dr. Rego noted the same in vines
up to 18 years old, and Dr. Pascoe in vines up to 24 years old.
That is why Dr. Ferriera called it slow die back. Its
not so much that the dying is slow, but that the onset of symptoms
can take many years.
One small bit of good news is that polymerase chain reaction (PCR)
testing is coming of age for the Phaeos (but not Cylindrocarpon)
and promises to be faster and more reliable than current tests.(2)
The actual test takes only two days, though normal lab logistics
and reporting require seven to 10 days, but that is far faster than
the six to eight weeks required for culture testing. More important,
PCR testing is nearly 100% accurate, compared to 60% for culture
How did these pathogens come in under the radar? As was the case
at Pearl Harbor in World War II, the radar was switched off. Since
Dr. Petris work in 1912, little was being done to check for
fungal pathogens in rootstocks until quite recently.
What may be the biggest factor in widespread disease is the worldwide
planting boom starting in the late 1980s, which continues today.
When demand outpaces supply, quality standards tend to decline,
and the product follows. Substandard vines that should be burned
are instead planted and grow poorly, if at all. Again, it is up
to growers to motivate nurseries to improve the quality
of their planting material.
One researcher has suggested that the new rootstocks
may be more susceptible to young vine decline than AXR-1 was, due
perhaps to the partial-vinifera parentage of AXR-1. This is doubtful,
as Dr. Petri noted dark gummosis in AXR-1 in Sicilian vines that
were in decline without phylloxera.(1) In any
case, rather than begging the question, research would need to be
done to confirm this conjecture. However, it is a moot point as
growers do not have the option to use AXR-1 due to its fatal flaw
There is no option but to use American rootstocks.
Management and stress
Environmental stresses and/or mismanagement are often blamed for
vines that perform very poorly. Growers are often brushed aside
with vague maybes, such as, Maybe you have a soil
problem or Maybe you irrigated too much (or too little)
or Maybe you have a nematode problem or Maybe
the weather was too hot (or too cold) when you planted (unlike
Goldilocks, conditions are never just right) or
and this one is usually the clincher Maybe this is
the wrong rootstock for this site. This list of maybes
is far from exhaustive.
What is clear is that growers can do their best to minimize stress,
but their vines would not be so sensitive to stress if they were
not diseased. Adverse weather and other stresses exacerbate the
problems associated with these fungal diseases, but the fundamental
problem is disease, not stress.
Regarding stress, Dr. Smart notes, Such interactions are so
obvious to the astute observer as to require little comment. Certainly
any organism, be it plant or animal, weakened by a stress, be it
environmental or pathological, is more predisposed to disease. However,
sometimes the symptoms are confused, and the inexperienced might
blame the unknown problem solely on the environmental stress, for
which the symptoms are commonly better-known.(3)
Some have noted that propagating rootstocks is extremely stressful.
To this viticultural consultant, Lucie Morton responds, There
is no question that if vines are infected with black goo, they are
much more vulnerable to any stress, including the process of grafting.
However, grafting is necessary
and healthy vines have many
strategies for surviving stress. Diseased vines are greatly handicapped.(1)
This argument about the practical importance of stress is
eerily reminiscent of the 1970s-era academic conjecture that phylloxera-susceptible
AXR-1 could be recommended as long as it was confined to less
stressful sites with irrigation and deep fertile soils.
Lack of stress did not save AXR-1 from phylloxera, and lack of
stress cannot be counted on to save vines from black goo, although
it may delay the onset of decline for a number of years.
Finally, great wines are most often associated with sites
of low fertility and low water-holding capacity that is sites
with somewhat stressful conditions.
In a recent report on California grapevine materials, Lynn Alley
et al. (UC Davis) noted: Virus and virus-like diseases have
probably existed in Californias vineyards from the earliest
years, but were poorly understood at the time and often went unrecognized
Diseases caused by virus or bacteria-related problems were
often attributed instead to unsound viticultural practices. In a
1931 book proposal, Frederic T. Bioletti, first head of the UC Department
of Viticulture, addressed the issue of vine problems in a chapter
entitled, Vine Troubles Attributed to Climatic, Soil, and
Cultural Conditions. The UC Davis report then noted
that the diseases that Bioletti was dealing with were actually leaf
roll virus, fanleaf virus, and Pierces disease.(4)
Those who would attribute young vine decline to environmental stress
and/or cultural practices should learn from Biolettis example.
Proponents of the stress hypothesis must also explain the very uneven
distribution of failing vines compared to those showing normal to
very vigorous growth (see Figure 1).
What stress did the stunted vines experience that their healthier
counterparts nearby did not?
Why are failing vines intermixed with productive vines? What stress
results in a shotgun pattern of dying, stunted, weak,
and thriving vines? Such patterns are more easily explained by having
healthy vines mixed in with vines infected with various pathogens
on planting day as illustrated in Tables I
Michael Porter worked as a winemaking assistant
and as a research assistant at Crocker Nuclear Lab, UC Davis while
studying physics at Cal State University, Chico. He earned a masters
degree in earth sciences from Chico. He has taught geology, meteorology,
oceanography, physics, and astronomy in junior colleges. Since 1984,
he has provided soil fertility, vine nutrition, and water management
- Wines & Vines, November 1995, p. 46, Mystery
Diseases Hit Young Vines, Lucie Morton.
- Wines & Vines, January 1997, p. 62, Update
on Black Goo, Lucie Morton.
- Practical Winery & Vineyard, May/June 1998, p. 32,
Young Grapevine Decline in California, Heather Scheck
- Practical Winery & Vineyard, November/December 1998,
p. 5, Another Disease Looming? Richard Smart.
- Black Goo, Symptoms and Occurrence of Grape Declines,
edited by Lucie Morton, 1999, International Ampelographic Society,
Healdsburg, CA, and Santa Rosa Junior College libraries. If
checked out, try the reserve desk.
(To order a copy, cost is $29.95 plus $5 shipping/handling, contact
IAS/ICGTD, fax: 540/933-6987, email@example.com).
- Phytopathologica Mediterranea, Special Issue on Esca and
Grapevine Declines, 2000, Mediterranean Phytopathological
Union, Healdsburg, CA, and Santa Rosa Junior College libraries.
If checked out, try the reserve desk.
(To order a copy, cost is $67.25 plus $5 shipping/handling, contact
IAS/ICGTD, fax: 540/933-6987, firstname.lastname@example.org).
to get vines tested
- Glenn Friebertshauser, Agri-Analysis, 45133 Co. Rd. 32-B, Davis, CA
95616, tel: 530/757-4656, email@example.com
- Sharon Harney, Forensic Analytical Laboratory, 2959 Pacific Commerce
Dr., Rancho Dominguez, CA 90221,
- Diana Fogle, Plant Pest Diagnostics Branch CDFA, 3294 Meadowview Road,
Sacramento, CA 95832 tel: 530/262-1100.
- James Stamp Consulting Service, 1212 Beattie Ln., Sebastopol, CA 95472,
tel: 707/829-8405, firstname.lastname@example.org.
- UC/USDA Laboratory by way of your UC Cooperative Extension farm advisor.
- Black Goo, Symptoms and Occurrence of Grape
Declines, edited by Lucie Morton (see above).
- Phytopathologica Mediterranea, Special Issue
on Esca and Grapevine Declines, Mediterranean Phytopathological
Union (see above).
- Slow Dieback of Grapevines, Strauss
Ferriera, 1994, South African Jrnl of Enology & Viticulture.
- Retrospective on California Grapevine Materials,
part II: Problems facing Californias growers, Lynn Alley,
Deborah Golino, and Andrew Walker, 2001, Wines & Vines.