Description and Biology

Alternaria black spot or Alternaria rot is caused by Alternaria spp. and is not considered a major disease. It typically occurs as a secondary issue in fields where strawberry fruit have been left over-ripe in the field or damaged by hail, excessive mite injury, natural cracking, or other sources of physical or biological wounding. The fungus does not cause primary injury but instead colonizes and grows on already damaged fruit.

Symptoms on fruit appear as small, irregular spots that are slightly sunken and appear light green to black in color as spores grow on the spot. These symptoms may look similar to other major fruit diseases, such as Anthracnose Fruit Rot of Strawberry.

Management of Alternaria black rot includes removing over-ripe fruit from the field, minimizing wounding, and managing mites.

Mite management:
Cyclamen Mites in Strawberries
Twospotted Spider Mite

Figure SS-1: Alternaria black spot on strawberry showing lesion in fruit colonized by the black mold that also has a greenish hue.

Frank J. Louws

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Figure SS-1: Alternaria black spot on strawberry showing lesion in fruit colonized by the black mold that also has a greenish hue.

Frank J. Louws

Figure SS-2: Alternaria black spot on strawberry showing lesions on fruit colonized by Alternaria alternata with a dark black moldy appearance.

Frank J. Louws

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Figure SS-2: Alternaria black spot on strawberry showing lesions on fruit colonized by Alternaria alternata with a dark black moldy appearance.

Frank J. Louws