DISEASES OF GRAPEVINE

Описание: DISEASES OF GRAPEVINE
DOWNY MILDEW
Causal organism: Plasmopara viticola
Sub-division: Mastigomycotina
Symptoms
Irregular, yellowish, translucent spots on the upper surface of the leaves. Correspondingly on
the lower surface, dirty white, powdery growth of fungus appears. Affected leaves become,
yellow and brown and gets dried due to necrosisInfected leaves, shoots and tendrils are
covered by whitish growth of the fungus.White growth of fungus on berries which
subsequently becomes leathery and shrivels. Infected berries turn hard, bluish green and then
brown and show soft rot symptom. No cracking of the skin of the berries.
Fig 11.1: Downy Mildew of Grapevine
Disease cycle
Primary infection: Sporangia or zoospores by wind, rain etc.
Secondary infection: Oospores present in the infected leaves, shoots and berries. Also as
dormant mycelium in infected twigs
Favourable conditions
• Optimum temperature: 20-22°C.Relative humidity: 80-100 %.
Management
 Collect and burn fallen leaves and twigs.
 Sanitation of the orchard..
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 Vine should be kept high above ground to allow circulation of air by proper
spacing.
 Sprays with 1% Bordeaux mixture or Copper oxychloride.
11.2 POWDERY MILDEW
Causal organism: Uncinula necator (I.S: Oidium tuckeri)
Sub-division: Ascomycotina
Symptoms
Small whitish patches appear on both the surface of the young leaves. These patches
enlarge covering the leaf surface with a characteristic, whitish powdery coating. In
advanced stage affected leaf turn greyish white and become dwarf ,twisted and
malformed.Floral infection results in shedding of flowers,discolouration of flower and
poor fruit set.Powdery growth is visible on older berries and the infection results in
the cracking of skin of the berries.
Fig 11.2: Powdery Mildew of Grapevine
Disease cycle
Primary infection: Through dormant mycelium and conidia present in the infected shoots
and buds.
Secondary infection: Through air-borne conidia.
Favourable conditions
 Cool dry weather.
 Maximum temperature in the range of 27-310C with R.H. upto 91% favourable
disease. (November and December).
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Management
 Clean cultivation of vines or removal and destruction of all diseased parts.
 Spray wettable sulphur @0.3% or karathane or calixin @0.1%.
11.3 ANTHRACNOSE / BIRDS EYE DISEASE OF GRAPEVINE
Causal organism: Elsinoe ampelina (I.S: Gloeosporium ampelophagum)
Sub-division: Ascomycotina
Symptoms
Circular, greyish black spots with yellow halo appear on leaves. Later the centre of the spot
becomes grey, sunken and fall off resulting in a symptom called „shot hole‟. Sunken spots
with ashy grey centre and dark margin on fruits (Birds eye symptom). In warm and wet
weather pinkish spore mass develop in the centre ofthe spots. Mummification and shedding
of berries
Fig 11.3: Birds eye disease of Grapevine
Disease cycle
Primary infection: Survives as dormant mycelium in the infected stem-cankers.
Secondary infection: Through conidia by air or water.
Favourable conditions
 Warm wet weather
 Low lying and badly drained soils.
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Management
 Removal of infected twigs.
 Selection of cuttings from disease free areas .Spraying Bordeaux mixture 1% four
times in a month from the time of pruning and ending prior to fruit maturity.
 Spray Carbendazim + Mancozeb @ 0.2%.