Diseases Flashcards
How does phylloxera kill vines?
It feeds on the roots, which then allows pathogens that live in the soil an entryway. It’s infection by pathogens that kills the vines.
What rootstock was famously thought to be phylloxera resistant but wasnt?
AXR1
Name two parasites that feed on roots.
Phylloxera vastatrix
Nematodes
What spreads fanleaf virus?
a nematode called Xiphinema index, aka dagger nematode
How can soils with nematodes be treated?
- Leaving the soils fallow for several year
- certain rootstocks are resistant
- mustard as a cover crop is believed to be helpful
What vectors leafroll virus?
Mealybugs
Name two insects that damage the fruit directly.
Suzukii fruit fly
European grapevine moth
Name three vine maladies native to N America
Phylloxera vastatrix
Powdery mildew
Downy mildew
What is Oidium?
Powdery mildew
What is Erysiphe necator?
powdery mildew/oidium
What is the most critical time to control oidium/powdery mildew?
Bud break and flowering because infection can spread quickly on immature plant tissue
What is Plasmopara viticola?
Downy mildew
What is downy mildew often called in Europe?
Peronospora
How is powdery mildew spread? And Downy?
Powdery mildew spores are carried by wind.
Downy mildew is carried by water (more often seen in places that get summer rain)
What is Bordeaux misxture and what does it treat?
Copper and sulfur, sprayed to treat both powdery and downy mildew
Name two kinds of bunch rot.
Botrytis
Sour rot
What is the ideal weather pattern for botrytis?
Rainy spring, 65-75ºF
Rain near harvest
Dry conditions during harvest to prevent secondary infection.
Name three trunk diseases
Esca
Eutypa Dieback
Botryosphaeria
What are the symptoms of Esca?
Tiger-striped leaves and black measles on the berries
How do trunk diseases spread?
They enter the vine through pruning wounds, dirty pruning tools
What causes black rot?
Guignardia bidwellii
What causes Pierce’s disease?
Xylella fastidiosa bacteria
How does Pierce’s disease harm vines?
infects the xylem of the vines, preventing the transport of water.
Why is Pierce’s disease more common in California than Europe?
in part at least because of Europe’s colder winters
Name a phytoplasmic disease
Flavescence dorée
How does Flavescence doree harm the vine?
A type of bacteria that infects the plant’s phloem, which transports sucrose and amino acids from the leaves to the rest of the plant
What are signs of Flavescence doree?
aka "grapevine yellows" Delayed, abnormal shoot growth discolored leaves that curl downward dehydrated berries green, unlignified shoots in the fall
What spreads Flavescence doree and other phytoplasmic diseases?
Leafhoppers
Name three bacterial diseases
Pierce’s disease
Crown gall
Bacterial blight
How does crown gall spread?
Usually in the nursery during grafting
Name three viral diseases
Leafroll virus
Fanleaf virus
Red Blotch disease
What are the symptoms of leafroll virus?
Leaves roll downward
Red varieties leaves turn red, white leaves turn yellow
Significantly lower yields
Delayed maturation
What spreads leafroll virus? What is used to stop it?
Mealybugs
Sexual confusion
Removed infected vines
What are the symptoms of fanleaf virus?
Asymmetric leaves
yellow mosaic pattern on the leaf
Millerandage
Reduced yield and quality
What spreads fanleaf virus?
Usually introduced by infected rootstock and then spread by nematodes, which are very hard to get rid of. Nematode resistant rootstock can be used,
