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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Fruit > Grape > Spots/blotches/other discoloration

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Grape > Leaves > Spots/blotches/other discoloration

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  • Image: Black Rot 1
  • Image: Black Rot 2
  • Image: Black Rot 3

Black Rot
Guignardia bidwellii

  • Leaves have round tan spots with dark edges, tiny black pimples are often visible in the center of the spot
  • Black slightly sunken ovals or short streaks can be seen on Infected young green vines, leaf and flower stalks
  • A red ring appears on berries, this grows quickly until the entire berry is brown
  • Berries that have been infected for several days dry up, shrink and wrinkle into a bluish black ‘mummy’ that remains attached to the cluster
  • Multiple berries in a cluster can be infected
  • Symptoms on berries commonly show up when the fruit is half grown
  • More information on Black Rot...
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  • Image: Downy Mildew 2
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  • Image: Downy Mildew 1

Downy Mildew
Plasmopara viticola

  • Yellow-green “greasy” lesions develop on upper leaf surface
  • Lower leaf surface develops a dense, white cottony growth under humid conditions
  • Infected green fruit turn light brown to purple are soft, covered in a downy felt, and easily fall off the cluster
  • Berries are most susceptible when pea-size (early summer) and again when approaching maturity (late summer, early fall)
  • More information on Downy Mildew...
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  • Image: Anthracnose 2
  • Image: Anthracnose 1
  • Image: Anthracnose 3

Anthracnose (Bird’s Eye Rot)
Elsinoe ampelina

  • Leaves develop circular lesions with gray centers and brown or black margins, the center of the leaf spot may fall out resulting in small ragged holes in the leaf
  • Infected shoots develop spots that become sunken lesions with gray centers and dark reddish-brown raised edges
  • Infected shoots may be confused with hail damage; but unlike hail damage, the edges of the lesions are raised and black
  • Berries develop small, reddish circular spots that average 1/4 inch in diameter that may become sunken with a dark brown to black margin, resembling a “bird’s eye”
  • Berries are susceptible from bloom to veraison
  • Infection is more prevalent in rainy years
  • More information on Anthracnose (Bird’s Eye Rot)...
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  • Image: Botrtyis 3
  • Image: Botrtyis 1
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Botrytis
Botrytis cinerea

  • Leaves have large, red-brown patches; a gray mold may or may not be observed on the leaf
  • Berries become soft and watery, and may be covered in a fuzzy white-gray mold
  • White grapes will start to turn brown while purple grapes turn reddish in color
  • Berries that have been infected for several days will shrivel and drop to the ground as hard mummies
  • Multiple berries in a cluster can be infected
  • More information on Botrytis...
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  • Image: Phomopsis 2
  • Image: Phomopsis 1
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Phomopsis Cane and Leaf Spot
Phomopsis viticola

  • Leaves may be puckered along the veins or the margins may be turned under
  • Dark brown spots with yellow edges can also appear along leaf veins and petioles, the lower leaves are most commonly affected
  • Fruit will turn light brown and shrivel, small raised black pimple like structures may be visible on the fruit surface
  • Symptoms on berries are most obvious close to harvest on maturing fruit
  • More information on Phomopsis Cane and Leaf Spot...
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  • Image: Powdery Mildew 2
  • Image: Powdery Mildew 3
  • Image: Powdery Mildew 1

Powdery Mildew
Uncinula necator

  • Upper leaf surface develops white or grayish-white patches
  • Berries may be misshapen, covered by the white, powdery growth and often split open
  • Infected berries have a rusty spots; red varieties develop a blotchy appearance at harvest
  • Can be more prevalent in drier conditions
  • More information on Powdery Mildew...
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  • Image: Leafhoppers 1
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Leafhoppers

  • Leaves develop pale yellow to white blotches, mostly near leaf margins
  • Severe feeding may cause leaves to curl downward
  • Leafhoppers are present from June through August
  • Leafhoppers feed on the underside of leaves
  • More information on Leafhoppers...
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  • Image: Nutrient Deficiency 1

Nutrient Deficiency

  • Leaves turn yellow, but the veins remain green (interveinal chlorosis)
  • Prevalent in iron-deficient soils
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  • Image: Tomato Ringspot Virus 1

Tomato/Tobacco Ringspot Virus Decline

  • Leaves exhibit a random pattern of yellows and greens or leaf yellowing in first year of infection
  • Smaller leaves, shorter internodes, and reduced yield are evident in second year
  • Growth is severely stunted in the third year
  • Fruit clusters are sparse with uneven ripening
  • More information on Tomato/Tobacco Ringspot Virus Decline...

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