diseases of grapes

FUNGAL DISEASES

1. Downy mildew : Plasmopara viticola2. Powdery mildew :Unicnula nectator3. Bird’s eye spot/Anthracnose : Elsinoe ampelina4. Brown spot : Cercospora viticola5. Grey mould : Botrytis cinerea6. Blue mould : Pencillium digitatum

Yellowish, translucent spots appear on upper surface of leaves.

White fungus growth appears on berries

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.

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.

Epidemology

Disease development is favoured during :

Heavy dew

Relative humidity 80-100%

Temperature 23- 27°C :t

Management

Spray Bordeaux mixture 1% (or)

Metalaxyl + Mancozeb 0.3 to 0.4 % (or)

Difolation 0.25% (or)

Chlorothalonil 0.2%

Powdery growth mostly appears on upper surface of leaves

Powdery growth on older berries

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.

`

Mode of spread and survival

The fungus spreads through air borne conidia.

Epidemology

Warm condition with sultry weather is favourable for disease development.

Heavy rain has an adverse effect on disease development.

Management

Proper pruning should be followed.

Spraying Wettable sulfur 0.2% (Or)Carbendazim 0.1% (or)Dinorcap 0.7% effectively controls disease

Resistant varietiesRed sultan , Saint george

Young shoots are more susceptible than leaves

Circular, greyish black spots appear.

Spots become circular, sunken, ashy grey colour surrounded by dark margin.

Bird’s eye appearance

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

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.

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

Epidemology

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

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.

Blue mold on grapes

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

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