Q. My apples have black marks on them. I thought this was a disease, but I can wipe it off when I scrub it. What is this?
Twylah from Poland
A. Backyard fruit production is no easy task. At our fruit tree pruning clinics, we push “air and sunlight reduces disease pressure” as the main focus for home gardeners trying to produce fruit in their gardens.
But in a year like this it is difficult to win the battle against diseases.
The two diseases present on Twylah’s apples were sooty blotch and fly speck. Sooty blotch makes an apple look like it’s covered in black soot (thus the name). If you try to wash it with a cloth or rub it with your finger, the fungus can be wiped away. Thankfully, this disease does not affect the inside of the fruit. It can be quite a challenge to clean it all off of the fruit, but it is still edible.
The second disease is fly speck, named because it looks like flies have left their “dots” on the fruit like they do on the white siding of many homes and other surfaces during the summer. But this is, in fact, a fungus. What you see are the fruiting bodies of the fungus. They are not as easy to rub off as sooty blotch.
Both diseases are favored in years like we’ve had this year: lots and lots of moisture, and periods of cool, yet humid, weather.
To reduce the presence of these and most fungal diseases in the home orchard, home gardeners must plan before planting trees. Choose a sunny location with lots of good air circulation. If the tree already exists, work on pruning. Do not prune more than 25 percent of the tree each year. Prune to a central leader system. If you have a large tree, it may be a losing battle. In that case, try to reduce the foliage in the center of the tree and prune during the season to increase air flow through the tree canopy and sunlight penetration as much as possible.
A great resource for home fruit production is the Midwest Home Fruit Production Guide, complete with 269 color photos/ illustrations to show you how to get your best fruit production. It covers all berries, tree fruit and more. Call our office or stop by to purchase a copy.
Eric Barrett is the Ohio State University Extension educator for agriculture and natural resources in Mahoning County. Call the office hotline, 330-533-5538, from 9 a.m. to noon Mondays and Thursdays to submit your questions.