Diseases, Pests Flashcards
Phytoplasma Diseases
Flavescence Doree
Fungal Diseases
- Powdery Mildew
- Downey Mildew
- Eutypa Dieback
- Esca
- Black Rot
- Bunch Rot
Young shoots develop dark brown streaks and eventually wither and die.
Bacterial Blight
Powdery Mildew
Powdery mildew affects all green parts of the plant, marking grapes, leaves, and shoots with its dusty white mildew growth. If infected prior to flowering, yields will be reduced; if infected after fruit set, berries will struggle to achieve veraison and reach full size. Fruit affected by powdery mildew is universally avoided in the winemaking process, as it creates off-flavors in the wine.
Black Rot
The disease is caused by the Guignardia bidwelli fungus, originating as a black spot on the vine’s shoots, leaves, and berries. Although yield reductions can be disastrous if unchecked, the disease can be controlled through fungicide sprays.
Deformed shoot growth with poor fruit set and shot berries. Leaves are malformed and may display yellow bands.
Fanleaf degeneration
Bacterial Diseases
- Pierce’s Disease
- Crown Gall (Black Knot)
- Bacterial Blight
Bacterial Blight
Bacterial Blight often kills young grapevine shoots. They develop dark brown streaks in early spring, and eventually wither and die. Spread by rain and compromised pruning tools, the disease can be controlled by hot water treatments and copper sprays, such as the Bordeaux Mixture.
Eutypa Dieback
Spores are carried by rain and enter the vine through pruning wounds. Infected vines experience stunted shoot growth as the fungus releases toxins, and eventually an infected cane may die—the dead arm.
Fanleaf Degeneration
A nepovirus spread by soil nematodes feeding on infected roots, severely curtails yields and affected vineyards must be removed. A complex of similar diseases, Fanleaf Degeneration deforms shoot growth, and leads to poor fruit set and shot (seedless) berries. The leaves on an infected vine are malformed, resembling fans in appearance, and may form yellow bands around the veins. The productive lifespan of the vine and its winter durability are diminished.
Fungal Diseases
- Powdery Mildew
- Downey Mildew
- Eutypa Dieback
- Esca
- Black Rot
- Bunch Rot
Spread by the glassy-wing sharpshooter and renders the plant incapable of producing chlorophyll.
Pierce’s Disease
Pierce’s Disease
Caused by the bacterium Xylella fastidiosa and most commonly transmitted by the glassy-winged sharpshooter—a leafhopping insect found near citrus orchards and oleander plants—Pierce’s Disease is a scourge, rendering vines incapable of producing chlorophyll and killing it within one to five years.
Viral Diseases
- Leafroll Virus
- Fanleaf Degeneration
Crown Gall (Black Knot)
When affected, a vine develops tumors (galls) on its trunk, which girdle and essentially strangle the vine, withering or killing outright the portions of the vine above. The bacteria thrive in colder climates, and systemically live inside the grapevine. During winter freezes, when the vine’s trunk may be ruptured, the bacteria invade the outer trunk, rapidly multiplying and fomenting the onset of disease. The disease is spread through the propagation of bacteria-infected budwood.