PEST & DISEASE MANAGEMENT

Question 1

Name the four most important fungal diseases

Answer 1

Downy mildew
Powdery mildew
Black rot
Grey mould (botrytis)

Question 2

Name the two most important vine virusses

Answer 2

Fanleaf virus
(Leafroll virus)

Question 3

Name the two most important vine bacterial diseases

Answer 3

Grapevine yellow (Bois Noir & Flavescence)
Pierce’s disease

Question 4

What is typical for downy mildew? (5)

Answer 4

Multiple cycles
Weather dependant
Risk as long as the stomata work
10-15 days incubation times
‘Oil’ spots on leaves and grey/brown rot on clusters

Question 5

What do the oospores of downy mildew need in order to germinate?

Answer 5

Min 11C in spring and rain. ‘Splash’ effect

Question 6

What is causing powdery mildew?

Answer 6

Erysiphe Necator, originally from north America

Question 7

What is typical for powdery mildew? (6)

Answer 7

Risky earlier in the season (with UV)
Multiple cycles
Attacts young leaves
Flag symptoms + grey/white powder on two sides of the leave
Need humidity (not especially rain)
No new infections after bunch closure

Question 8

What his causing black rot?

Answer 8

Guignardia Biwellii, originally from north America

Question 9

What is typical for black rot (4)

Answer 9

No new infection after stop growth
Maximum damage at fruitset
Mummification of berries + necrosis shoots
Multiple cycles –> needs rain

Question 10

What is typical for black rot (5)

Answer 10

No new infection after stop growth
Maximum damage at fruitset
Mummification of berries + necrosis shoots
Multiple cycles –> needs rain
10 Days incubation (=longer) so less cycles

Question 11

What is typical for grey mould? (4)

Answer 11

Causes problems for all kinds of crops
Latent phase between flowering and veraison (lazy mould goes for the juice!)
Needs rain
Infection at flowering, damage shown at veraison

Question 12

What can influence the level of damages? (5)

Answer 12

Weather
Timing of infection + multiplication rate
Viticultural practises (pruning/canopy etc)
Susceptibility of the variety
Quantity and quality of the inocuum

Question 13

Name 4 ways to manage diseases in the vineyard

Answer 13

Prophylaxis
Chemical control
Biological control
Resistant varieties

Question 14

What is the difference between contacts-/penetrating-/systemic fungicides?

Answer 14

Contact: no penetration / leachable
Penetrating: penetrating / leachable
Systemic: penetrating / not leachable / also for new organs

Question 15

When do you spray for downy mildew?

Answer 15

Between flowering and fruitset
At veraison

Question 16

When do you spray for powdery mildew?

Answer 16

Between flowering and bunch closure
Or when flag symptoms appear

Question 17

When do you spray the clusters for grey mould?

Answer 17

Flowering
Bunch closure
Veraison
Not recommended: 2-3 wk before harvest

Question 18

What is the vector of Fanleaf virus?

Answer 18

Infected nematodes in the soil
Xiphinema Index - can survive for 7 years
Many host plants

Question 19

Why is it so difficult to get rid of Fanleaf virus?

Answer 19

Because the vector can survive for 7 years in the soil also when the vineyard is uprooted.

Question 20

What is the vector for Flavescence Doree?

Answer 20

Infected leafhopper
Scaphoideus Titanus
Phytoplasma: Candidatus Phytoplasma Vitis (infected for life)

Question 21

How many generations does a leafhopper have per season?

Answer 21

Just one. So one spraying per year is enough.

Question 22

Why is it so difficult to treat against FD?

Answer 22

Minimum 1 year between inoculation and symptoms. When you realise it, it is too late. You can only treat the vector, not the disease

Question 23

What is the vector for Pierce’s disease?

Answer 23

Leafhopper & Xylella Fastidiosa
Blue-green sharpshooter
Green sharpshooter
Red-headed sharpshooter
Glassy-winged sharpshooter

Question 24

Why are the sharpshooters difficult to treat?

Answer 24

Because they don’t spend their whole lifecycle in the vineyard

Question 25

Name 3 closely related trunk diseases

Answer 25

Esca
BDA (black dead arm)
Apoplexy

Question 26

Can you cure trunk diseases?

Answer 26

No. They are infected for life. The necrosis wil spread over the years and eventually the vine will die. Till then you can still harvest grapes from this vines

Question 27

What causes eutypa dieback?

Answer 27

A fungus. Eutypa lata

Question 28

Why is eutypa dieback hard to treat?

Answer 28

Fungus is being spread by wind and rain
Vine is getting infected via pruning wounds
Fungus can survive on dead arm for 5 years
4-8 years of incubation time

Question 29

How do you see the difference between eutypa dieback and esca?

Answer 29

When you cut the trunk:
Esca: necrosis in the middle of the trunk
Eutypa: sectorial necrosis

Question 30

What is the vector of leaf roll virus?

Answer 30

Grape berry moths (3 generations)
Multiple generations
They host in grapes, piercing the skin and inducing grey mould

Question 31

What are the most important practical things to think of when spraying? (4)

Answer 31

Don’t spray with high wind (<20km/h)
Spray before the rain
Respect the renewal rates of the product
Control spray quality

Question 32

Which 4 treatments are mostly combined?

Answer 32

Downy mildew
Powdery mildew
Black rot
Insecticides for leaf hoppers
!! Only if allowed to mix

Question 33

What is the ‘bee label’?

Answer 33

Label at insecticides that are no harm for bees. Otherwise not allowed to spray during flowering (also not during flowering of the cover crop)

Question 34

What are ‘parasitoids’?

Answer 34

Insects that lay their eggs/larvae in the body of the pest species. It will not kill the host immediately, but it will make them less effective.

Question 35

What is a downside of pesticide use?

Answer 35

It will kill all insects, also the beneficial ones.

Question 36

What do we mean by ‘connectivity’?

Answer 36

The ability for insects/animals to move from one habitat to another.
Via trees/hedges for example.