News release: Sooty Blotch and Flyspeck of Apple

Tim Baker, MU Extension Horticulture Specialist
102 N. Main, Suite 1, Gallatin, MO 64640
660-663-3232, bakert@missouri.edu

Release Date: October 16, 2014

Headline: Sooty Blotch and Flyspeck of Apple

This fall, I’ve have been contacted on several occasions by homeowners who were worried about the apples from their orchards. Their apples had black, sooty-looking blotches all over. The blackened material was just superficial, and did not penetrate the skin.  It seemed to rub off with a bit of scrubbing. Were these safe to eat?

What these homeowners were dealing with is a fungal disease, commonly known as sooty blotch. A related disease is flyspeck. In the past, these were considered separate diseases. They are caused by a complex of several organisms. Some researchers now hold that they are different forms of the same disease.

The causal fungi overwinter on the twigs of apple trees and other woody host species. Spores are carried by raindrop splashing and wind to the fruit. Humid, rainy weather aids the spread of this disease. Optimal temperatures for fungal growth occur at 59-75 degrees. Hot, dry weather does not favor the development of sooty blotch or flyspeck. We certainly did see moisture and temperatures that were favorable to development of sooty blotch this year.

To control this disease, fungicides may be used.  For control recommendations, please refer to our Guide Sheet: Fruit Spray Schedules for the Homeowner.

Many of the people contacting me asked if the fruit could be eaten.  Since this is a superficial disease, and can be washed off, yes, it can be eaten after cleaning the fruit. Be careful to note that if something else has aided the penetration of the skin, the fruit may be rotted and should be discarded.

Although they can be eaten, apples that have been infected with sooty blotch or flyspeck may not keep well. That is because the fungus dissolves some of the protective wax. This wax naturally occurs on the apple, and prevents dehydration.  Thus, the apples may shrivel and not keep well.

If you would like more information on sooty blotch and flyspeck, please give me a call at 660-663-3232.  I have several guide sheets I can send to you.