PEST AND DISEASES
OF GRAPES
R.R.D.T. NIRANGA
Department of Horticulture & Landscape Gardening
Faculty of Agriculture & Plantation mgt
Wayamba University of Sri Lanka
Diseases
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Fungal
Powdery mildew
Downey mildew
Rust
Phomopsis cane and
leaf spot disease
Botrytis Bunch Rot
Pests
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•
•
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Bacteria
• Crown Gall of Grape
•
Viruses
• Grapevine fan leaf virus
• Arabis mosaic virus
• Rupestris stem pitting
virus
Grape Cane Borer
Mealy bug
Spider Mites
Berry eating
creatures
– Thief
– Wasps
– Ants
– Birds
– Squirrels
Vine girdler
Fungal Diseases
Powdery mildew (Uncinula necator)
Powdery mildew affected bunch & leaves
Powdery Mildew on Fruits
Severe powdery mildew
infection on grape leaf
Spore (conidia) production of
powdery mildew on a grape
leaf
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.
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
Downy Mildew (Plasmopara viticola)
Downy mildew on upper side of
grape leaf.
Downy mildew symptoms on a
shoot
Appearance of infection on
underside of a leaf
Downy mildew symptoms on fruits
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.
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
/Copper, Sovran, and Ziram
Botrytis Bunch Rot of Grape (Botrytis cinerea)
Discolored, shriveled berries
caused by Botrytis Bunch Rot
Botrytis cinerea sporulating
on grape berries
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
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
Phomopsis cane and leaf spot disease
(Phomopsis viticola)
Infected leaves
Infected inflorescence
Lesions of Phomopsis cane and leaf spot on
shoot and stem
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
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
Bacteria diseases
Crown Gall of Grape (Agrobacterium vitis)
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.
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
Pests of Grapes
Grape Cane Borer (Amphicerus bicaudatus)
Adult
Damage
Grape cane borer egg
Grape cane borer larva
Grape cane borer pupa
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
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.
Nutrient deficiencies
Boron deficiency
Potassium deficiency
Boron-deficiency