Diseases

Question 1

How does phylloxera kill vines?

Answer 1

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.

Question 2

What rootstock was famously thought to be phylloxera resistant but wasnt?

Answer 2

AXR1

Question 3

Name two parasites that feed on roots.

Answer 3

Phylloxera vastatrix

Nematodes

Question 4

What spreads fanleaf virus?

Answer 4

a nematode called Xiphinema index, aka dagger nematode

Question 5

How can soils with nematodes be treated?

Answer 5

• Leaving the soils fallow for several year
• certain rootstocks are resistant
• mustard as a cover crop is believed to be helpful

Question 6

What vectors leafroll virus?

Answer 6

Mealybugs

Question 7

Name two insects that damage the fruit directly.

Answer 7

Suzukii fruit fly

European grapevine moth

Question 8

Name three vine maladies native to N America

Answer 8

Phylloxera vastatrix
Powdery mildew
Downy mildew

Question 9

What is Oidium?

Answer 9

Powdery mildew

Question 10

What is Erysiphe necator?

Answer 10

powdery mildew/oidium

Question 11

What is the most critical time to control oidium/powdery mildew?

Answer 11

Bud break and flowering because infection can spread quickly on immature plant tissue

Question 12

What is Plasmopara viticola?

Answer 12

Downy mildew

Question 13

What is downy mildew often called in Europe?

Answer 13

Peronospora

Question 14

How is powdery mildew spread? And Downy?

Answer 14

Powdery mildew spores are carried by wind.

Downy mildew is carried by water (more often seen in places that get summer rain)

Question 15

What is Bordeaux misxture and what does it treat?

Answer 15

Copper and sulfur, sprayed to treat both powdery and downy mildew

Question 16

Name two kinds of bunch rot.

Answer 16

Botrytis

Sour rot

Question 17

What is the ideal weather pattern for botrytis?

Answer 17

Rainy spring, 65-75ºF
Rain near harvest
Dry conditions during harvest to prevent secondary infection.

Question 18

Name three trunk diseases

Answer 18

Esca
Eutypa Dieback
Botryosphaeria

Question 19

What are the symptoms of Esca?

Answer 19

Tiger-striped leaves and black measles on the berries

Question 20

How do trunk diseases spread?

Answer 20

They enter the vine through pruning wounds, dirty pruning tools

Question 21

What causes black rot?

Answer 21

Guignardia bidwellii

Question 22

What causes Pierce’s disease?

Answer 22

Xylella fastidiosa bacteria

Question 23

How does Pierce’s disease harm vines?

Answer 23

infects the xylem of the vines, preventing the transport of water.

Question 24

Why is Pierce’s disease more common in California than Europe?

Answer 24

in part at least because of Europe’s colder winters

Question 25

Name a phytoplasmic disease

Answer 25

Flavescence dorée

Question 26

How does Flavescence doree harm the vine?

Answer 26

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

Question 27

What are signs of Flavescence doree?

Answer 27

``` aka "grapevine yellows" Delayed, abnormal shoot growth discolored leaves that curl downward dehydrated berries green, unlignified shoots in the fall ```

Question 28

What spreads Flavescence doree and other phytoplasmic diseases?

Answer 28

Leafhoppers

Question 29

Name three bacterial diseases

Answer 29

Pierce's disease Crown gall Bacterial blight

Question 30

How does crown gall spread?

Answer 30

Usually in the nursery during grafting

Question 31

Name three viral diseases

Answer 31

Leafroll virus Fanleaf virus Red Blotch disease

Question 32

What are the symptoms of leafroll virus?

Answer 32

Leaves roll downward Red varieties leaves turn red, white leaves turn yellow Significantly lower yields Delayed maturation

Question 33

What spreads leafroll virus? What is used to stop it?

Answer 33

Mealybugs Sexual confusion Removed infected vines

Question 34

What are the symptoms of fanleaf virus?

Answer 34

Asymmetric leaves yellow mosaic pattern on the leaf Millerandage Reduced yield and quality

Question 35

What spreads fanleaf virus?

Answer 35

Usually introduced by infected rootstock and then spread by nematodes, which are very hard to get rid of. Nematode resistant rootstock can be used,