Bacterial Diseases in the Vineyard Flashcards
Explain Pierces Disease and its effect on the vine
Bacterial disease that quickly kills vines. The bacterium lives in the sap channels of vines, which it clogs, leading to shrivelling, dropping leaves and the death of the vine between one and five years. The bacterium is spread by the sharpshooter insect, which acts as a vector (an organism that transmits a disease). Chardonnay and Pinot Noir are more vulnerable.
How can you manage Pierces Disease?
There is no chemical control for the bacterium.
Control is by reducing the numbers of the vector. For example, removing vines close to rivers has been effective as riverbanks can be a habitat for one of the vectors, the blue-green sharpshooter. Some chemical insecticides can also be used. Introducing a species of wasp that feeds on the eggs of sharpshooters has also been effective.
Strict quarantine rules for the movement of plants have sought to prevent the further spread of the disease.
For the future, work is being done on developing Pierce’s Disease-resistant vines.
Explain Grapevine Yellow and its effect on the vine
A group of diseases caused by a type of bacteria. It is a serious threat to viticulture as there is no treatment available. The disease is spread by vectors, which include leafhoppers, and by nurseries selling untreated, diseased stock. Symptoms include delayed budburst, a drooping posture because the new shoots fail to become woody, and the canopy turning yellow (in white varieties) and red (in black varieties). In some strains, the vine dies as the disease progresses, in others it can recover after an attack. The economic impact is through drastically reduced yields and lower quality (high acidity and low sugar contents of grapes).
How can you manage Grapevine Yellow?
There is no control for grapevine yellows.
The focus is on controlling the vector. Leafhopper populations can be reduced by insecticides, and the plants that host the hoppers, including cover crops, should be removed.
Best practice in the nursery is to bathe the pruning wood in hot water to kill the disease.
