8. Hazards, Pests & Diseases

Question 1

What are management options for drought? (3)

Answer 1

1) irrigation systems
2) drought-resistant rootstocks
3) drought-tolerant varieties

Question 2

What happens during drought?

Answer 2

Loss of water = stomata closes = reduces photosynthesis

Question 3

What happens during excess water?

Answer 3

Leads to too much fungal growth = competes with grape ripening/too much shading = fungal diseases

Question 4

What are management options for excess water? (1)

Answer 4

Plant on slope/free draining soil

Question 5

What happens during untimely rainfall?

Answer 5

• during pollination/fruit set = millerandage or coulure
• mid season = reduce the rate of ripening fruit (you want water deficiency at this time)
• close to vintage = grapes swell with water = splitting = grey rot

Question 6

What are management options for untimely rainfall? (1)

Answer 6

Monitoring forecasts and considering early harvest if necessary

Question 7

What are management options for winter freeze? (3)

Answer 7

1) Site selection (hillside is warmer, near water, where snow settles)
2) Choice of variety (ex. CF or Riesling)
3) Protecting vines (bury, build up soil around them, etc.)

Question 8

What are the two types of frosts?

Answer 8

1) Advective - caused by large volumes of cold air moving in from very cold areas
2) Radiative - result of heat being lost on cool, still nights

Question 9

What are management options for frost? (5)

Answer 9

1) Avoid frost pockets/choose hillside sites
2) Delaying pruning postpones bud burst into warmer months
3) Choose a variety that buds late
4) Vines high-trained off ground
5) Having bare soil between vines (absorbs more heat during day)

Question 10

What are some options to do when frost threatens? (3)

Answer 10

1) water sprinklers
2) wind machines
3) oil/propane gas burning heaters

Question 11

What are management options for hail? (3)

Answer 11

1) rockets can be fired into thunderclouds, seeding them with silver iodide causing rainfall instead of hail
2) net the fruit zone
3) select a number of plots in different areas

Question 12

What are management options for sunburn? (4)

Answer 12

1) row orientation and aspect
2) canopy management techniques to control amount of sun exposure
3) irrigation
4) agricultural sunscreen

Question 13

What are management options for fire? (3)

Answer 13

1) smoke detectors/sprinklers
2) water tanks
3) providing employee training in case of fire

Question 14

What are management options for smoke taint? (5)

Answer 14

1) affected musts can be tested analytically
2) how grapes are handled (since aroma precursors are present on inside of skins)
3) hand harvesting or gentle/whole bunch pressing, lower fermentation temperatures
4) flash detente
5) blending with unaffected wines

Question 15

What is phylloxera and what does it do?

Answer 15

• an aphid-like insect that feeds on and lays eggs on roots of grape vines
• weakens vine roots causing swelling and cracks, leading to rot

Question 16

What are symptoms of phylloxera? (5)

Answer 16

• vines die of drought in patches that increase each year
• vine roots are covered with insects and yellow eggs
• swellings in older roots
• pale green leaf galls on under-surface of leaves
• stunted shoot growth/leaf yellowing around 3 years – dies after 5

Question 17

What is the management option for phylloxera? (3)

Answer 17

• grafting onto American rootstocks
• heat treatment
• quarantine

Question 18

What are nematodes and what do they do? What are the two most common?

Answer 18

• tiny worms that are common in soil
• cause damage by feeding off vine roots and transmitting diseases
• decrease ability of plant to uptake water and nutrients
• two most common are root-knot and dagger

Question 19

What are management options for nematodes? (4)

Answer 19

1) leave soil to fallow for a number of years (but no crop present)
2) fumigate soil using chemicals (that are now banned in most regions)
3) plough in a cover crop of mustard plant
4) use nematode-resistant rootstocks

Question 20

What are grape moths and what do they do?

Answer 20

• moths that feed on flowers and grapes
• they create wounds that are susceptible to bacteria and fungi
• only larvae and females cause

Question 21

What are management options for grape moths? (2)

Answer 21

• insecticides
• biological controls such as bacteria that are toxic to moths, pheromone capsules that cause sexual confusion, and natural predators such as wasps

Question 22

What are spider mites and what do they do?

Answer 22

• species of mite differs from region to region in dusty conditions
• they feed on surface cells of leaves = discolouration = reduction in photosynthesis

Question 23

What are management options for spider mites?

Answer 23

1) make environment inhospitable by using sprinklers/cover crops to reduce dust
2) encourage predatory mites
3) general pesticides

Question 24

How does powdery mildew affect vines? What does it thrive in?

Answer 24

• it overwinters in buds/on canes then attacks young, green parts of the vine (grey patches to black patches)
• result of bud infections from previous year
• thrives in shady conditions and does not require high humidity
• CAUSED BY A FUNGUS

Question 25

What are management options for powdery mildew? (3)

Answer 25

1) keep an open canopy reduce shade/density of leaves
2) applications of sulphur
3) systematic fungicides

Question 26

How does downy mildew affect vines? What does it thrive in?

Answer 26

• caused by water mould that over-winters in vine tissue
• attacks green parts of plant
• needs rainfall and warm temperatures to spread

Question 27

What does downy mildew look like?

Answer 27

Yellow, circular “oil spots” on leads and then white, downy fungal growth on underside of leaves

Question 28

What are management options for downy mildew? (3)

Answer 28

1) sprays made from copper salts (ex. Bordeaux mixture)
2) other fungicides
3) good drainage and open canopy that dries quickly

Question 29

How does grey rot affect grapes? Which are most at risk?

Answer 29

• it affects any grapes with a point of entry
• spores are present in vineyard and become active in periods of rainfall and high humidity
• most affects varieties with thin skins and tight bunches

Question 30

What are management options for grey rot? (4)

Answer 30

1) selecting varieties with thick skins
2) protecting grapes against pests that can split skins
3) keeping open canopy and removing leaves around bunches
4) sulphur and copper are ineffective but other sprays can be used

Question 31

What is eutypa dieback?

Answer 31

• aka “dead arm”
• a fungal trunk disease that leads to rotten wood in vines and can affect whole vineyards
• infection occurs through pruning wounds in moderate temperatures during rain – spores spread by wind

Question 32

What are management options for eutypa dieback? (3)

Answer 32

1) pruning late and applying fungicide to pruning wounds
2) cutting affected trunks and burning dead wood
3) re-training from “sucker” but causes loss of yield for two years

Question 33

What is phomopsis?

Answer 33

A fungal disease that causes reduction in crops – infected canes whiten and break off easily

Question 34

What are management options for phomopsis?

Answer 34

1) fungicides applied 3 weeks after bud burst
2) diseased wood should be burnt and removed
3) best to prune early/late and not in rainy weather

Question 35

What is Esca? What are its symptoms?

Answer 35

• a complex fungal disease caused by. group of organisms that are prevalent in warmer/drier climates
• enters vine through pruning wounds
• symptoms include tiger-striping of leaves and spotting inside wood

Question 36

What is the management option for Esca? (1)

Answer 36

No chemical controls so prevention is key

Question 37

What is Pierce’s Disease and how is it spread?

Answer 37

• bacterial disease that quickly kills vines
• lives in sap channels of vines, clogging them, leading to shrivelling/dropping leaves and death between 1-5 years
• spread by leafhoppers (specifically sharpshooters)

Question 38

What are management options for Pierce’s Disease? (3)

Answer 38

1) reduce number of transmitters
2) quarantine and clean equipment
3) purchase clean stock

Question 39

What are the symptoms of grapevine yellows?

Answer 39

• delayed bud burst
• dropping posture
• canopy turning yellow (in white varietals) and red (in black varietals)

Question 40

How is grapevine yellows spread?

Answer 40

• vectors including leafhoppers

- nurseries selling infected stock

Question 41

What are management options for grapevine yellows? (2)

Answer 41

1) focus on controlling the vector
2) best practice in nursery is to bathe pruning wood in hot water
Note: there is no treatment available

Question 42

What is fanleaf virus and how is it spread?

Answer 42

• long standing group of diseases found around the world

- spread by move to grafted vines and dagger nematode

Question 43

What are the symptoms of fanleaf virus?

Answer 43

• early shoot growth is stunted
• canes grow in distorted ways
• leaves are very pale/look like a fan

Question 44

What is a management option for fanleaf virus?

Answer 44

There is no cure – before vineyards are planted, soil tests should be done to check for dagger nematodes

Question 45

What is leafroll virus? How is it spread?

Answer 45

• disease spread by grafting and mealy bugs

- doesn’t kill vines but can reduce yield by up to half by slowing down growth of roots and shoots

Question 46

What are management options for leafroll virus?

Answer 46

• there is no cure