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Damage to Fruit at Harvest

On this page
  • Botrytis bunch rot
  • Measles
  • Summer bunch rot
  • Non-botrytis slip skin
  • Western grapeleaf skeletonizer
  • Omnivorous leafroller
  • Grape mealybug
  • Vine mealybug
  • Thrips
  • Vinegar fly

Look for the following types of damage in your harvest sample. Note the presence of vinegar flies as an indicator of bunch rot diseases. Names link to more information on identification and management.

Click on photos to enlarge
Diseases and disorders

Botrytis bunch rot
Botrytis bunch rot
Identification tip: A berry infected with Botrytis bunch rot turns brown, splits, and leaks. As the disease progresses the infection spreads to other berries.

Identification tip: On berries, small, round, dark spots, each bordered by a brown-purple ring, may occur.

Summber bunch rot
Summer bunch rot
Identification tip: Examine clusters for masses of black, brown, or green spores that develop on the surface of infected berries.

Non-Botrytis slip skin
Non-Botrytis slip skin of ‘Redglobe’ grapes
Identification tip: Look for watery discoloration, presence of hairline cracks on berry surface and general berry breakdown.


Western grapeleaf skeletonizer
Western grapeleaf skeletonizer
Identification tip: Sunburned fruit resulting in the loss of quality can be a result of defoliation by western grape leaf skeletonizer.

Omnivorous leafroller
Omnivorous leafroller
Identification tip: Look for rotting and raisining (drying) of Thompson seedless grapes follows chewing damage by omnivorous leafroller larvae.

Grape mealybug
Grape mealybug
Identification tip: Examine clusters for cottony egg sacs, larvae, adults, and honeydew.

Vine mealybug
Vine mealybug
Identification tip: Honeydew and white wax on grapevines are often and indication of a vine mealybug infestation

Identification tip: Halo spots appear as small scars around sites where thrips punctured the grape to lay eggs.

Identification tip: Thrips feeding causes a starfish pattern of scarring on berries.

Vinegar fly
Vinegar fly adult
Identification tip: Adults (also called fruit flies) are small, yellowish flies that are commonly attracted to fermenting fruit of all kinds. They indicate the presence of bunch rot disease.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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