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

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on November 16, 2018. The information contained within may not be the most current and accurate depending on when it is accessed.