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| I have two hedge rows of holly (Ilex Blue Maid? Not sure). One section is covered in black ... mildew? This section gets shade in the winter and was weighted down by lots of snow for weeks. After the snow melted, we had lots of rain.
The trunks are covered in the black stuff, as well as the leaves. This stuff seems to have spread to leaves on other sections. I do realize that there needs to be more air circulation, I was just starting a major pruning when I saw this for the first time.
What is this "stuff" and what would you suggest I do? Thanks for any insights. Maureen |
Follow-Up Postings:
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- Posted by gardengal48 PNW zone 8 (My Page) on Tue, Mar 23, 10 at 10:09
| Assuming this "black stuff" scrapes off easily? If so, most likely sooty mold, a substance that grows on the excretions ('honeydew') of sucking insects, like aphids or scales. The sooty mold in and of itself is harmless, unless it is a very heavy infestation that can interfer with photosynthesis (yours is pretty darn close!). What you need to determine is what insect is causing the problem with the honeydew and address treatment there. btw, sooty mold washes off relatively easily, although you may need some hands-on attention to the foliage to do a thorough job. |
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- Posted by maureeninmd z6 MD (My Page) on Tue, Mar 23, 10 at 10:30
| Gardengal - It scrapes off pretty easily. I should have noted that the hollies seem healthy otherwise. So it must be honeydew as you suspected. Thanks. Could this problem take care of itself, i.e., wash off eventually? Do you think these sucking insects are really damaging something? I don't use pesticides. I do not know where the little suckers are hiding. My garden is a bit of a jungle. I photographed the worst of the sooty mold. I suppose I should be looking UP from the problem. I see a giant blue spruce, a very tall narrow pine, a very large holly tree. There are also some small deciduous trees but they haven't leafed out yet. |
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- Posted by gardengal48 PNW zone 8 (My Page) on Tue, Mar 23, 10 at 11:29
| The two issues do not necessarily occur simultaneously. The insect problems most likely were present last summer, with the sooty mold developing later. And often it is an entirely different plant hosting the insects with the honeydew dropping down from above. Check the spruce for aphids, otherwise it may well be one of the deciduous trees and you will need to keep checking as the season progresses. IME, the sooty mold does not wash off satisfactorily with just rain water or irrigation - you need a pretty strong, directed stream to get rid of it. Any birches in the area? They are notorious hosts for aphids, so much so to the extent that it is not a good idea to plant them where one has a patio, deck or driveway underneath, as the honeydew dripping down gets all over everything. |
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- Posted by maureeninmd z6 MD (My Page) on Tue, Mar 23, 10 at 12:36
| No birches here, but I will keep an eye out for whatever is dripping all over this hedge. I am so relieved that the problem is not with the hollies as this hedge gives me wonderful privacy. I would feel truly ill if this was a lethal problem. Thank you for all of your help today. |
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| There are so many insect suspects that could contribute to the black sooty mold problem. How are you on insect identification? Scale insects of many kinds could create the honey dew excrement, as can whitefly, and aphids. I agree that you might look UP to see what might be lurking in the trees nearby. Scale insects can be observed now, if you know what you are looking for. Aphids will come into the picture as soon as buds turn into new growth. |
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