What are the symptoms of young vine decline?
The vine may grow more slowly, have a smaller trunk and have
less foliage than normal. Leaves may be yellowed and wilting,
and the root system is diminished. A cross section of the
rootstock will reveal dark-brown or black spots.
What causes young vine decline?
It's caused by a group of five fungi including one species of
a fungus known as Phaeomoniella and four species of a fungus
known as Phaeoacremonium.
How does it affect the vines?
Vines can be infected by spores produced by these fungi,
which can enter through wounds made on the vines during
propagation and through pruning wounds during the dormant
season in vineyards. Once infection has occurred, the fungi
invade the water-conducting tissue of grapevines and may
cause the affected tissue to dry due to plugging of the
After infection, the plant recognizes the fungal infection
in its vascular tissue, which transports water and nutrients.
The plant then seems to try to wall off the invading fungus
in the vascular tissue, producing dark gums and vessel-
blocking cells called tyloses.
How did this disease get the nickname "black goo"?
In some cases, young vine decline causes the sap in the
infected vines to turn dark brown or black.
How contagious is it?
The fungi that cause young vine decline can be found in most
vineyards. The concern is not only over transmitting the
fungus, but causing stress that will result in disease.
What triggers an outbreak of disease in a vineyard?
It appears that environmental stresses such as inadequate
irrigation water or fertilizer, improper planting or
producing a crop of fruit on very young vines can trigger
development of the disease.
Does it affect plants other than grapevines?
Does it occur in other winegrape-growing regions
of the world?
Yes, young vine decline has been observed in California,
Italy, France, South Africa, Portugal and Australia. It was
first reported in Italy around 1900.
How long has it been a problem in California?
The earliest report of the fungi involved in California
occurred in the late 1950s. It has been a concern in the
state's major winegrape-producing regions since the early
What is the estimated economic impact?
Researchers estimate that 1 percent of vineyards in
California's North Coast may be affected by the disease.
However, only rarely does an entire vineyard show symptoms;
rather, there are usually areas in the vineyard with weak
plants. Unfortunately, some growers have pulled their entire
vineyard when the disease occurred, regardless of whether
symptoms occurred vineyard-wide.
How does it compare to other diseases affecting
Although young vine decline is definitely a concern to
California grape growers, it currently affects only an
estimated 1 percent of the state's vineyards. It is much less
of a potential threat to the state's grape industry than
either the Phylloxera louse or Pierce's disease, caused by
the glassy-winged sharpshooter.
How can growers prevent it?
The best way to prevent young vine decline is to eliminate
the environmental stresses that seem to trigger the disease.
Growers should provide plenty of irrigation water and
fertilizer, make sure that the rootstocks are planted
properly and delay production of a crop until at least the
What can be done once a vineyard is infected?
There currently are no successful methods of treatment other
than to replace vines that show symptoms of the disease.
Aren't there fungicides that can be used to control
What can nurseries do to prevent its spread?
Eliminating vines or rootstock that carry the fungi may not
practical because the fungi are so widespread and appear to
commonly live within grapevine tissue. Nurseries should make
sure that they sell only vines that are otherwise healthy and
protected from debilitating environmental stresses.
Fungicide use may offer some protection in nurseries and in
vineyards. Protection wounds might offer limited defense
against infection. Hot-water treatments have been evaluated
and not proven to be useful in stopping invasion by the fungi
or in cleaning up infected wood. UC Davis researchers and one
nursery are experimenting with vacuum infiltration of fungicides.