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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis
sootyblotch of apple

Sooty Blotch of Apple

Posted by John Fulton -

Apple development seems to be running ahead of normal this year. Sooty blotch and flyspeck are caused by different fungi that commonly occur together on the same fruit. The sooty blotch fungus causes surface discoloration with black spots or blotches which can be a fourth of an inch or larger. These spots may run together, making the apple appear to be covered with something like charcoal dust. This disease is more superficial than anything, since it is only on the skin. Vigorous rubbing, or scrubbing, will remove the black discoloration. If you want to be sure, you can always peel the apples.

This disease is most common with moderate temperatures and wet weather. Wet weather can include heavy dews which don't get dried out very well. Anything that cuts down on air circulation helps promote sooty blotch. Pruning and thinning fruit will help improve air circulation, and lessen the disease problems.

The best chemical control program is to use a multi-purpose fruit tree spray, containing captan fungicide, as a preventative. For this disease, it is recommended to begin by early June, and continue the program until harvest. For the organic gardeners, sulfur will help some. However, it is not as good as the captan. Remember many diseases are preventable in home fruit production, but they are not curable. Once you see the problem, it becomes a to-do list item for next year.

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