Greenhouse experiments have
demonstrated that Cylindrocarpon obtusisporum, Phaeoacremonium
chlamydosporum, P. inflatipes, and P. aleophilum are
aggressive pathogens of grape seedlings (fig. 1). Seedlings
are used for bioassays because they can produce symptoms rapidly and are
certain to be disease-free at the beginning of a trial.
seedlings (Vitis vinifera Carignane) were inoculated by
dipping their roots in a 106 spore/ml suspension for 30 minutes. After 60 days,
75% of seedlings inoculated with Cylindrocarpon obtusisporum, 50% with
Phaeoacremonium aleophilum, 63% P. chlamydpsporum, and 56% with
P. inflatipes, had died. The pathogens were easily recovered from both
the roots and the stems of the moribund seedlings. Control plants treated with
water remained healthy, and pathogens were never detected.
Field inoculations to confirm
Phaeoacremonium as a pathogen of young vines were done at UC Davis. In
August 1994, own-rooted grapevines (Vitis vinifera
Chardonnay) were inoculated with a 106 spore/ml suspension and
planted in 3.8L pots. Spores were introduced by drilling a small hole into the
crown and filling the hole with spores or cutting the roots, then dipping the
vine into the spore suspension for 30 minutes. Control plants were treated in
the same manner but were inoculated with sterile water.
In February 1995, these vines were
planted in the field. In October 1997, the test grapevines were removed from
the field and destructively sampled. Both inoculation methods gave similar
results, and the data were combined for analysis.
All inoculated grapevines were
visibly stunted with small chlorotic leaves. The vascular elements and the pith
near the crowns of inoculated vines were discolored. The caliper of the wood,
measured at 2.5 cm above the soil line, was 28 mm for the control vines,
compared to only 13 mm for inoculated vines, a reduction of more than 50%. (See Table III).
The dry weight of leaves and petioles
was approximately three times less and the dry weight of wood was approximately
four times less in the vines inoculated with P. chlamydosporum compared
with water-inoculated controls.
|Table III - Effect of
Phaeoacremonium chlamydosporum on own-rooted Chardonnay grapevines.*
|Caliper (mm) ^
|Leaves and petioles # (g)
|Wood ## (g)
|* After innoculation,vines were planted and grown for 2.5
years at the UC Davis Plant Pathology farm.
** Mean of five replications
^ Caliper of 1997 wood measured 2.5 cm above the soil line.
# Leaves and petioles were removed and dry weights were taken after four days
in a 38°C drying oven.
## 1997 wood weights after four days in a 38°C drying oven.
Weve demonstrated the ability
of Phaeoacremonium inflatipes, P. chlamydosporum and P.
aleophilum. to survive in nutrient-poor sand for over 28 days. It is
possible that these pathogens are introduced into the grape rootstocks during
the callusing stage of nursery production.
In the callusing process, cuttings
are removed from cold storage and placed in heated bins of sand, sawdust, or
peat moss for 25 to 48 days. The wounded end of the cutting forms a callus
layer and initiates rooting. Small pathogen populations might be introduced
into the callusing trays from infected cuttings. Once in the warm, damp media,
they could spread through the callusing tray.
We have begun research with
assistance of two commercial nurseries to determine whether these pathogens
infect vines during commercial production of nursery stock.
Fungi in the genera
Cylindrocarpon and Phaeoacremonium have been consistently
isolated from young grapevines showing decline symptoms. Cylindrocarpon
spp. are generally recognized as relatively weak pathogens on vegetables,
small fruits, tree fruits, forage, ornamentals, and conifers and therefore of
limited economic importance. Production of chlamydospores allows the pathogen
to survive in soil for extended lengths of time in the absence of a suitable
Cylindrocarpon destructans has
been identified as causing a disease of young vines in France known as
black-foot. One California isolate of Cylindrocarpon was identified as
C. destructans in 1994. Since 1994, C. obtusisporum has been the
most commonly isolated species.
However, because of the similarities
in symptom expression caused by the two closely related species of
Cylindrocarpon, we propose to maintain the name black-foot
disease for decline caused by either species. We propose the name
Phaeoacremonium grapevine decline to define the symptoms
associated with infection by Phaeoacremonium spp.
Hence two new diseases of young
grapevine have been identified in California: black-foot, caused by
Cylindrocarpon obtusisporum or C. destructans; and
Phaeoacremonium grapevine decline, caused by as many as three species of
Fungi in the genus
Phaeoacremonium have also been implicated as the pathogens in
black measles or esca disease of older grapevines
(Vasquez and Gubler, unpublished data). Black measles is a destructive disease
of woody tissues in grapes and has an extensive range of symptoms. These
include stunted growth and dieback, leaf chlorosis and necrosis, raisining of
fruit, plugged xylem vessels, and occasionally sudden wilting and/or death of
vines. Black measles symptoms have been seen in some young vines infected with
These organisms have been in
California for many years, and it is unclear why pathogens formerly associated
only with older grapevines have recently emerged as a threat to young
grapevines. Cultural practices or environmental conditions may have shifted in
favor of the pathogens.
For example, at several sites,
grapevines that were exposed to low temperatures in the winter of 1990/1991
have showed typical decline symptoms. Alternatively, perhaps new strains of
these pathogens have evolved, or perhaps the huge planting boom has simply
increased awareness of young vine decline.
Thus far, no obvious relationship
exists between rootstock or scion varieties and the severity of either
Cylindrocarpon black foot disease or Phaeoacremonium grapevine
decline. Because of the phylloxera epidemic, AXR-1 rootstock, used almost
exclusively for 20 years, has been replaced by other rootstock varieties. The
new rootstocks may prove to be highly susceptible to these diseases,
particularly if pre-disposed by devigorating conditions. Investigations into
differences in susceptibility and symptom expression in rootstock varieties are
Due to the similarity of symptoms,
diagnosis of Cylindrocarpon black foot disease or Phaeoacremonium
grapevine decline should never be made solely on the basis of visual symptoms.
Young grapevines can fail for many reasons, including poor nutrition, improper
irrigation (too much or too little), poor planting techniques, virus-induced
incompatibility, nematodes, and poor quality planting stock.
Vascular symptoms can also have many
biotic and abiotic causes. Black or amber streaks seen in the vascular elements
are the result of deposition of phenolic compounds in response to wounding, a
general defense mechanism of the plant. Physical injuries to the grapevine due
to root tearing, disbudding, or other trauma during production or planting can
result in phenolic depositions and black discoloration, or even outright death
Other terms have been used in the
popular press to describe the visual symptoms of phenolic deposition and
formation of gums and tyloses in the vascular tissues, including black
goo and black xylem disease. These names do not encompass the
full range of symptoms associated with Cylindrocarpon black foot disease
or Phaeoacremonium grapevine decline nor do they provide a description
of the problem adequate enough to be of value to plant pathology or to the
Our lab at UC Davis is focusing on
increasing our understanding of pathogen biology, disease epidemiology, and
symptom development in Cylindrocarpon black foot disease and
Phaeoacremonium vine decline. Studies are underway to determine how
these pathogens survive and spread. Sources of pathogen inoculum will be
identified. Eventually, with an increased understanding of the disease biology,
effective control strategies can be developed.
1. Maluta, D.R. and P. Larignon 1991. Pied-noir: Nieux vaut
prevenir. Viticulture 11: 71-72.
2. Grasso, S, and G.M. Lio 1975. Infezioni de Cylindrocarpon
obtusisporum su piante di vite in Sicilia. Vitis 14: 1, 36-39.
3. Scheck, H.J., S.J. Vasquez, P. Larignon, D. Fogle, and W.G. Gubler, 1997.
Cylindrocarpon black-foot disease and Phaeoacremonium
grapevine decline in California. California Agriculture, in press.
1. Ferreira, J.H.S., P.S. Van Wyk, and
E. Venter 1994. Slow dieback of grapevine: Association of Phialophora
parasitica. S. Afr. J. Enol. Vitic. 15: 9-11.
2. Crous, P.W., W. Gams, M.J. Wingfield, and P.S. van Wyk, 1996.
Phaeoacremonium gen. associated with wilt and decline diseases of
woody hosts and human infections. Mycologia 88: 786-796.
Heather J. Scheck is a post-doctoral
scholar, Stephen Vasquez is a graduate student, and W. Douglas Gubler is an
extension plant pathologist, all with the University of California, Davis.
Diana Fogle is an agricultural biological technician at the California
Department of Food & Agriculture, Sacramento. This research was funded in
part by the California Grape Rootstock Commission and Grapevine Improvement