Diseases of grapes

pathological diseases in grapes

2. FUNGAL DISEASES
1. Downy mildew : Plasmopara viticola
2. Powdery mildew :Unicnula nectator
3. Bird’s eye spot/Anthracnose : Elsinoe ampelina
4. Brown spot : Cercospora viticola
5. Grey mould : Botrytis cinerea
6. Blue mould : Pencillium digitatum

4. Yellowish, translucent spots appear
on upper surface of leaves.
White fungus growth
appears on berries

6. Symptoms
Initial irregular, yellowish, translucent spots appear on upper
surface of leaves.
The lower surface of leaves show white powdery growth of
fungus.
The infected leaves turn brown resulting premature defoliation.
White fungus growth appears on berries and berries wrinkle and
show reddish brown discolouration.
The infected fruits become mummified later.

7. Mode of spread & survival
The sporangia of fungus spreads through wind,rain etc.
Fungus survives as oospores in infected leaves, shoots and
berries.
The dominant mycelium survives in twigs.

8. Epidemology
Disease development is favoured during :
Heavy dew
Relative humidity 80-100%
Temperature 23- 27°C
:t

9. Management
Spray Bordeaux mixture 1%
(or)
Metalaxyl + Mancozeb 0.3 to 0.4 %
(or)
Difolation 0.25%
(or)
Chlorothalonil 0.2%

11. Powdery growth mostly appears on upper
surface of leaves
Powdery growth on older berries

12. Symptoms
Powdery growth mostly appears on upper surface of leaves
Floral infection results in shedding of flowers and poor fruit set.
Powdery growth on older berries and infection results in severe
cracking of berries.
`

13. Mode of spread and survival
The fungus spreads through air borne conidia.

14. Epidemology
Warm condition with sultry weather is favourable for disease
development.
Heavy rain has an adverse effect on disease development.

15. Management
Proper pruning should be followed.
Spraying Wettable sulfur 0.2%
(Or)
Carbendazim 0.1%
(or)
Dinorcap 0.7% effectively controls disease
Resistant varieties
Red sultan , Saint george

17. Young shoots are more susceptible than leaves
Circular, greyish black spots appear.

18. Spots become circular, sunken, ashy grey colour surrounded by dark
margin.
Bird’s eye appearance

19. Symptoms
Symptoms seen on leaves, stem, tendrils, berries
Young shoots are more susceptible than leaves.
Initially circular, greyish black spots with yellow hallow appear.
Later these spots become circular, sunken, ashy grey colour
surrounded by dark margin.(bird’s eye appearance).
Black ,sunken lesions appear on young shoots.
Severe infection leads to mummification of berries

20. Etiology
The anamorph of the fungus is Gloeorporium ampelophagum
which produees hyaline ,single celled conidia.
The telemorph of the fungus is Elsinoe ampelina which produces
hyaline 4 celled ascospores.

21. Mode of survival and spread
The fungus spreads through infected vine cuttings and air borne
conidia.
The fungus survives as dormant mycelium in the infected stem-
cankers

22. Epidemology
Heavy rains after pruning and warm wet weather favour the
disease development

23. Management
Removal of infected twigs.
Spraying Bordeaux mixture 1%
(or)
Copper oxychloride 0.25%
(or)
Captafol 0.2%
(or)
Mancozeb 0.25% manages the diseases effectively.

25. Blue mold on grapes

26. SYMPTOMS
Scanty growth - white and turn bluish green are
seen.
Decay the berries
Infected tissues become soft and watery
Infected berries emits a moudly flavour

27. Management
Avoiding injuries to the ripe berries helps to reduce soft rot.
Clean planting stock; (ii) Disease wood removal and
immediate burning; (iii) fungicide application at shoot
extension and later if temperatures are cool. Sulphur is said
to reduce new infections in the early Spring