POWDERY MILDEW (Oidium) Flashcards
1
Q
Causative organism
A
Erysiphe necator
2
Q
LEAVES
A
- first signs, upper surface
- small pale yellow spots
- white, powdery fungal gorwth develop
- normal physiological functions seriously hampered
- intense: early leaf fall (bunch exposure/heat damage)
- reserve accumulutaion compromised
3
Q
SHOOTS
A
- superficial powdery growth
- Irregular spots on green shoots (become darker when they rubbed)
- retained with lignification
- observed on winter canes
- dieback/limited growth
- buds on these canes have problems with bud burst
4
Q
BUNCHES - when
A
from flowering to just before the grapes are ripe
5
Q
Also known as
A
Wit roes
6
Q
Affected areas?
A
Green parts. Shoot, leaves, bunches
7
Q
Inflorescences
A
- wilt
- poor or no berry set
8
Q
Small berries
A
- green berries rapidly covered in white powder
- turn brown
- dropped or develop unevenly
9
Q
Bigger berries
A
- white powderiness WITH
- brown corking on the surface
- under powdery dust: darker colour scars present
- berries burst and expose seeds
10
Q
Affected pedicels
A
hamper translocation of nutrients to such an extent ripening can not take place
11
Q
How does Oidium happen
A
no water required for the germination of the spores
the spores hibernate in winter buds and are released during bud burst.
