Fungal%20Diseases

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Fungal Diseases
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Powdery mildew (Uncinula necator)
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Powdery Mildew on Fruits
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• Symptoms
• Powdery mildew produces white, powdery growth on
• grape leaves and shoots.
• Severely infected leaves may turn brown and fall
  off.
• Infected berries appear rusty or scaly.
• They may fail to mature properly or split open.

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• Ecology
• The fungus survives the winter in infected grape
  tissue.
• Wind carries spores long distances.
• Unlike most other fungus diseases, powdery
  mildew
• tends to be most severe in dry growing
  seasons.
• Management
• Cultural Management
• Less susceptible to powdery mildew.
• Plant grapes in full sun with good air
  circulation
• Fungicides

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Downy Mildew (Plasmopara viticola)
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• Symptoms
• Infected leaves develop yellowish-green, and
  translucent
• oily lesions on their upper surfaces.
• On lower surfaces, the fungus produces a white
  to grayish
• cotton-like growth.
• Affected leaves eventually turn brown, wither,
  curl, and
• drop early, exposing the immature berries to
  direct sun.
• Berries that are infected when young turn light.
  
• Ecology
• Spores are spread by splashing rain, wind, and
  through
• The handling of plants.

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• Management
• Cultural Management
• When planting grapevines, select sunny, open
  areas with
• good air movement.
• Prune and train vines annually to maintain
  excellent air
• circulation
• Control tall weeds and grasses in the planting
  area.
• Fungicides
• If downy mildew is a problem, a program of
  fungicide
• sprays may be needed.
• Captan, Copper compounds, (fixed coppers and
• Bordeaux mixture), Mancozeb, Ridomil/MZ,
  Ridomil

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Botrytis Bunch Rot of Grape (Botrytis cinerea)
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• Symptoms
• Ripening grapes are affected by a rot
• With sufficient rain and humidity, berries split
  open and
• develop a grayish mold on the surface.
• Affected berries may shrivel in the dry climate.
• Ecology
• Infection is optimal at 15-20oC with free water
  or over
• 90 humidity. 
• Grape cultivars with dense canopies, thin skins,
  and/or
• tight clusters are more susceptible to
  botrytis bunch
• rot

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• Management
• Cultural Management
• Prevent excessive vine growth by judicious use
  of water
• and fertilizer.
• Prevent berry damage (powdery mildew birds and
  insects)
• Canopy management
• Fungicides

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Phomopsis cane and leaf spot disease (Phomopsis
viticola)
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Lesions of Phomopsis cane and leaf spot on shoot
and stem
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• SYMPTOMS
• Phomopsis cane and leaf spot appears as tiny
  dark
• spots with yellowish margins on leaf blades
  and veins
• Basal leaves with heavy infection become
  distorted
• and usually never develop to full size
• On shoots, small spots with black centers
  similar to
• those found on leaves occur usually on a
  basal portion
• of the shoot
• Heavy infection usually results in a scabby
  appearance
• of the basal portions of the shoot

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• Control
• Cultural practices
• Increase air circulation in the vineyard
• Removing diseased canes from the vine during
  normal
• pruning operations
• This disease can be controlled by applying
  protectant
• fungicides before rainy weather begins
• Chemical control
• Contact materials such as copper, sulfur, ziram,
• mancozeb, and maneb

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Bacteria diseases
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Crown Gall of Grape (Agrobacterium vitis)
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• Symptoms
• Gall formation on the aerial part of the vines
• Young galls are soft, creamy to greenish in
  color, with no
• bark or covering.
• As they age, the tissue darkens to brown.
• The surface becomes open and the texture becomes
• moderately hard and very rough
• Ecology
• Spread through propagation of diseased wood.

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• Management
• Cultural Management
• Select sites with good air and water drainage
• Avoid vine stress due to poor nutrition or low
  pH
• pest control programs for nematodes
• Do not propagate wood taken from galled vines
• Hot water treatment of vines is effective in
  reducing crown
• gall infection levels in planting materials
• Fungicides

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Pests of Grapes
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Grape Cane Borer (Amphicerus bicaudatus)
Adult
Damage
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Grape cane borer egg
Grape cane borer larva
Grape cane borer pupa
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• Damage
• Small holes can be seen on the vine
• Bore the vine and weaken the vascular functions
• Vine become weak and dry
• Management
• cultural practices
• such as removal and destruction of affected
  canes
• Chemical practices

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Spider Mite (Tetranychus pacificus)

• Damage
• Mites feeding on the undersides of the leaves
  may
• cause foliage to turn a bronze color.
• Leaf bronzing early in the season causes
  stunting and
• reduces berry quality.

• Management
• Cultural Management
• Good irrigation and fertilizer practices help
  offset
• damage to foliage.

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Nutrient deficiencies
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Boron deficiency
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Potassium deficiency
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Boron-deficiency
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