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 vessels. 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? No. 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 1990s. 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 California vineyards? 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 third year. 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 this disease? No. 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. Why is this disease difficult to control? It is caused by so many different and widespread fungal species, and its epidemiology is not fully understood. What research needs to be done in order to develop control strategies? Researchers need to further examine the biology of the fungi and ways in which they trigger the disease to develop.