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.
Flavescence Dorée is a _______________
Phytoplasma Disease
Leafroll Virus
Leafroll Virus, a condition caused by a complex of at least nine different viruses, may be responsible for as much as 60% of the world’s grape production losses. Although affected vines display radiant shades of red and gold in the autumn, such beautiful colors, combined with a characteristic downward curling of the leaves, signal the virus’s malevolent side: reduced yields and delayed ripening. Leafroll Virus, spread through propagation of infected vines or by an insect vector like the mealy bug, is currently incurable but it will not kill the vine; thus, infected vines are not always removed.
Esca (Black Measles)
Esca is the result of a complex of fungi, rather than a single organism. On young vines, the disease will weaken growth, affect berry development and discolor leaves; in hot weather an affected young vine may suddenly die. In older vines, the disease affects the wood, causing the interior of the trunk and arms to soften and rot from the inside—a condition that led ancient Romans to use Esca-infected tree trunks for firewood, as its spongy interior quickly caught fire. Mature, Esca-infected vines will rarely live past 30 years of age. The disease is exacerbated by rainfall and can be spread by wind or on the pruning shears of careless vineyard workers.
Four main groups of diseases affecting vines
- Fungal
- Bacterial
- Viral
- Phytoplasma
Bunch Rot
In general, bunch rots reduce crop yields and may adversely affect the character of the wine, imbuing it with moldy off-flavors. One of the most common forms of bunch rot is Botrytis bunch rot. Known in its malevolent form as grey rot, the Botrytis cinerea fungus will break down the skin of berries and allow other yeasts and bacteria to rot the grapes. It spreads quickly throughout vineyards. However, if the fungus invades healthy white grapes under favorable conditions, it will instead result in the noble rot, a precondition for some of the world’s greatest sweet wines. Botrytis bunch rot requires warm weather and humidity of at least 90% to germinate.
Flavescence Dorée
A form of grapevine yellows,. Leafhopper insects and propagation of infected vines spread the disease, which will initially delay budbreak and slow shoot growth, eventually causing bunches to fall off the vine and berries to shrivel. The disease will discolor leaves, cause pustules and cracks to form, and may kill young vines. No cure exists, although insecticides may be used to control leafhopper insect populations and retard its spread.
Responsible for at least %60 of the world’s crop loss, signs include a downward rolling of the leaf combined with vibrant autumn colours.
Leafroll Virus
Infected canes display stunted growth and eventually die. Some wineries have found an upside to this disease as the affected cane produces concentrated fruit before dying.
Eutypa Dieback - “Dead Arm”
Downy Mildew
Plasmopara viticola, the agent of downy mildew, attacks the green portions of the vine, causing leaves to drop off the vine and limiting the vine’s ability to photosynthesize. The infection is first visible as an oil spot on vine leaves. As spores germinate a white, cottony growth develops on the underside of the leaves. The fungus survives the winter on fallen leaves in the soil, and its spores reach the vine again with the help of rain splatter in the spring. Arid regions prohibit its growth.
Tumors on the trunk that strangle and may outright kill the vine above.
Crown Gall (Black knot)
In which country has leaf-roll virus been a significant problem?
South Africa
