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| I have a huge harvest of apples from my Jonathan apple tree this year. Not only is there an unbelievable amount, they are huge in size from all the rain we've had this summer. However, as always, the apples, although they have no dimples or insect infestation, are covered with black sooty spots. I have always blamed this on fly ash from the neighboring power plants. My son in law has informed me that he thinks the spots are powdery mildew. My question is how can I tell?? Our ag. extension office is too far away to take them to be analyzed. Is there something I can do to identify these spots? If I wash them and scrub them with an abrasive sponge the marks do come off and the water is grey. I would rather it be a natural cause than pollution! |
Follow-Up Postings:
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- Posted by harvestman 6 (My Page) on Sun, Oct 19, 14 at 19:32
| It is sooty blotch, a summer fungus almost as reliable in the east as summer rain. Pretty good year for it, but for a Jonathon that's pretty bad. Maybe you should prune your trees more open. Takes 3-5 summer sprays to prevent it but it is harmless and usually most of it can be wiped off with a nylon pad. |
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- Posted by Ferroplasm 7b (My Page) on Sun, Oct 19, 14 at 22:01
| I see fly speck on there, too. Do these two often accompany one another? |
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- Posted by nyRockFarmer (My Page) on Sun, Oct 19, 14 at 23:06
| The amount depends on the type of apple and the length of time the apples are wet. Where I'm at, sooty blotch doesn't really form until September when the nights are cold enough to form condensation on the apples. From there, it depends on how quickly the apples dry off during the day. If the apples are out in full sun with good airflow, there will be less of it. If they are covered by foliage or there are a lot of overcast days, there will be more of it. This September was unusually dry here (< 1"), but I only got a few apples due to previous winter's bud damage. I had a single Empire apple out in an open area of the tree and it didn't have any sooty blotch or flyspeck. A tree of unknown variety had some apples at the very top with a hint of sooty blotch and some flyspeck (see below). Another tree of unknown variety had apples tucked well inside the dense canopy that looked only slightly better than the one pictured above. |
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- Posted by harvestman 6 (My Page) on Mon, Oct 20, 14 at 6:31
| NY Rock, In southeast NY the issue starts well before Sept and I have to begin spraying for it in July. I've never heard of it being a purely late summer issue when reading about its management. The condensation issue may play a part in the problem when it's dry in mid-summer, but I doubt it is the crux of the issue in the northeast when August and July get "normal" rain. This year rain events were short, often at night and August was pretty dry. Conditions and pressure vary greatly year to year. Some years early varieties, like Ginger Gold or Gravenstein don't get it, and other years they are hammered. If you are correct you could control it with a single spray there in Sept. Here, I usually don't even need to spray in Sept. Why would condensation be more damaging than heavy dew, which occurs all summer long in the northeast? |
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| Thank you so much for the info. If only I had posted years ago when I first noticed it! Although coal burning power plants are a concern, especially in our area, it's very reassuring to know that this ugly soot is not to be blamed on them. |
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