Sooty Blotch and Flyspeck on Apple

This fall we had numerous calls and emails about the unsightly look of apple fruit in the home orchard. This disease is known as sooty blotch and flyspeck, a fungal disease that only affects the appearance of the apples.

These apples have sooty blotch and flyspeck. A ruler is shown to convey size of fungus.
These apples have sooty blotch and flyspeck. A ruler is shown to convey size of fungus.

Sooty blotch and flyspeck is considered a complex of several fungi that usually occur on the same fruit. Sooty blotch appears as superficial, dull black spots or blotches that may merge to cover most of an apple. Flyspeck appears as clusters of 6 to 50 or more slightly raised, black shiny round dots that resemble fly excreta (frass).

Because the fungi that cause sooty blotch and flyspeck grow superficially on the surface of the fruit, losses are primarily through lowered quality. (The black discoloration can be removed by vigorous rubbing.)

Several cultural practices aid in the control of sooty blotch and flyspeck. Pruning, which facilitates drying, has been shown to reduce disease incidence and severity. The value of pruning, however, is somewhat dependent on the season. It appears to help more in dry seasons than wet seasons. Proper thinning of fruit is also helpful. These tactics combined with the use of protectant fungicide sprays can help reduce the cosmetic damage on the fruit.

Can the fruit be eaten? See the article Can Sick Plants Make People Sick?

Originally prepared by Paula Flynn, updated by Lina Rodriguez Salamanca

Authors: 

Lina Rodriguez Salamanca Extension Plant Pathologist and Diagnostician (Program Specialist II)

Dr. Lina Rodriguez Salamanca is an extension plant pathologist and diagnostician with the Iowa State University Plant and Insect Diagnostic Clinic, a member of the North Central Plant Diagnostic Network (NCPDN) and National Plant Diagnostic Net...

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