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#1
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[IBC] Powdery mildew on oak(Quercus robur)
Looks like I have a case of mildew on an English oak. This is
the first time I've seen this. It started as small yellow dots on the leaves of a branch in the apex, now those leaves are covered in yellow and distorted. Now other leaves are showing yellow dots. Powdery mildew isn't yellow, and I have NEVER heard of it on an oak! Tho the page you supplied says it does infect oaks -- in Europe, at least -- it also doesn't indicate that it's yellow. Powdery mildew is a gray "dust" on leaves, and that's what the picture seems to show. The page also suggests some fungicides, but if you have lime sulfur on hand, it should do the trick (IF it is powdery mildew!!!!!). Jim Lewis - - Tallahassee, FL - Who has several crape myrtles with PM (in the yard -- and they're about to get cut down!) ************************************************** ****************************** ++++Sponsored, in part, by Mike Page ++++ ************************************************** ****************************** -- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ -- +++++ Questions? Help? e-mail +++++ |
#2
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[IBC] Powdery mildew on oak(Quercus robur)
This tree was wintered outside last winter(buried + mulched). Seven other Q. robur were wintered in a garage and show no sign of mildew. That shouldn't have made a difference, unless the other trees stayed in the garage during the spring infection period, or unless the buried tree was mulched in infected oak leaves. I suppose I could defoliate the tree either gradually or completely(this hasn't been done for a few years on this tree). Powdery mildew isn't harmful on oaks (it's more unsightly than anything else); what you should do is to wait until fall and remove the leaves as they senesce; those yellow dots are the over-wintering stage, and will be infective next spring. Any ideas on a fungicide or baking soda solution? Too late for this year; next year you could treat the leaves prophyllactically, but home-recipe baking soda won't work on oak leaves; you should buy a formulated baking soda fungicide with adjuvants to allow better penetration, or find a fungicide labeled for powdery mildew on ornamentals. Nina, who just took her applicator's license test, hence use of words like "prophyllactic" and "adjuvant". ************************************************** ****************************** ++++Sponsored, in part, by Mike Page ++++ ************************************************** ****************************** -- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ -- +++++ Questions? Help? e-mail +++++ |
#3
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[IBC] Powdery mildew on oak(Quercus robur)
Powdery mildew isn't yellow, and I have NEVER heard of it on an oak! Powdery mildew is common on oak, but the "powdery" stage is hard to see- whereas the sexual state is large and distinct. It starts out bright yellow, and then, as it matures, it turns chestnut brown. The Tulasne brothers, pioneers in plant pathology, figured out that the powdery stage and the sexual stage were parts of the same organism in 1861, and the "Father of Mycology", Anton de Bary, nailed the details in 1863. I am very proud to be an academic descendant of de Bary's, since my chair was a student of Fitzpatrick, who was a student of one of de Bary's students. Nina, who is now studying the genus Phytophthora, which De Bary named in 1876. ************************************************** ****************************** ++++Sponsored, in part, by Mike Page ++++ ************************************************** ****************************** -- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ -- +++++ Questions? Help? e-mail +++++ |
#4
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[IBC] Powdery mildew on oak(Quercus robur)
Powdery mildew isn't yellow, and I have NEVER heard of it on an oak! Powdery mildew is common on oak, but the "powdery" stage is hard to see- whereas the sexual state is large and distinct. It starts out bright yellow, and then, as it matures, it turns chestnut brown. The Tulasne brothers, pioneers in plant pathology, figured out that the powdery stage and the sexual stage were parts of the same organism in 1861, and the "Father of Mycology", Anton de Bary, nailed the details in 1863. I am very proud to be an academic descendant of de Bary's, since my chair was a student of Fitzpatrick, who was a student of one of de Bary's students. Nina, who is now studying the genus Phytophthora, which De Bary named in 1876. OK. Wow, I try to learn something new every day! Today, it got fed to me (hope that counts). I guess my books don't like to talk about sex. FORGET WHAT I WROTE! Listen to Dr. Nina! Jim Lewis - - Tallahassee, FL - "People, when Columbus discovered this country, it was plum full of nuts and berries. And I'm right here to tell you the berries are just about all gone." -- Uncle Dave Macon, old-time musician ************************************************** ****************************** ++++Sponsored, in part, by Mike Page ++++ ************************************************** ****************************** -- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ -- +++++ Questions? Help? e-mail +++++ |
#5
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[IBC] Powdery mildew on oak(Quercus robur)
Nina,
Thanks, I'll follow your advice. All this mycology is way more complicated than bonsai! Now, if I can just find out what ate the truffles(mushrooms), in the pots. Those nasty little squirrels no doubt! Best regards, Alan Blue Mountain Bonsai Ontario, Canada Zone 6 |
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