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Treating powdery mildew in potted rose
[cross-posted to rec.gardens]
Hi all - I recently potted a new John F. Kennedy rose that is about 3.5 feet tall and has multiple canes with a few buds which are about to open. A lot of the leaves, especially at the top of the canes, are curling at the edges and have a white cast to them, which from my online research looks just like powdery mildew. What would be the best way to treat that in a potted rose? Should I remove all the infected leaves and cut back the canes, or try to treat it with fungicide first? It would be a shame to cut it back severely -- the bush has a nice upright shape and strong, healthy canes. Also, I read that neem oil shouldn't be applied when temps are over 90 degrees; does that mean it shouldn't be used in hot weather at all, or just not actually applied to the leaves when the temp is above 90? Thanks in advance for any assistance. Rhonda Richmond, VA USDA Zone 7 ********* Basic human psychology is one of my subroutines. |
#2
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Treating powdery mildew in potted rose
"Natty Dread" wrote in message
.. . [cross-posted to rec.gardens] Hi all - I recently potted a new John F. Kennedy rose that is about 3.5 feet tall and has multiple canes with a few buds which are about to open. A lot of the leaves, especially at the top of the canes, are curling at the edges and have a white cast to them, which from my online research looks just like powdery mildew. What would be the best way to treat that in a potted rose? Should I remove all the infected leaves and cut back the canes, or try to treat it with fungicide first? It would be a shame to cut it back severely -- the bush has a nice upright shape and strong, healthy canes. Also, I read that neem oil shouldn't be applied when temps are over 90 degrees; does that mean it shouldn't be used in hot weather at all, or just not actually applied to the leaves when the temp is above 90? Thanks in advance for any assistance. Rhonda Richmond, VA USDA Zone 7 I have one rose that occasionally gets powdery mildew and I tend to use the organic solution - baking soda. Check out the article at the American Rose Society for a variety of solutions: http://www.ars.org/About_Roses/disease_powdery1.htm I can't comment on the use of neem oil over 90 degrees, first because I've never used neem oil, second because it's hard to find daily temps *below* 90 degrees around here during the growing season! Gail near San Antonio TX Zone 8 |
#3
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Treating powdery mildew in potted rose
"Gail Futoran" wrote in message ... "Natty Dread" wrote in message .. . [cross-posted to rec.gardens] Hi all - I recently potted a new John F. Kennedy rose that is about 3.5 feet tall and has multiple canes with a few buds which are about to open. A lot of the leaves, especially at the top of the canes, are curling at the edges and have a white cast to them, which from my online research looks just like powdery mildew. What would be the best way to treat that in a potted rose? Should I remove all the infected leaves and cut back the canes, or try to treat it with fungicide first? It would be a shame to cut it back severely -- the bush has a nice upright shape and strong, healthy canes. Also, I read that neem oil shouldn't be applied when temps are over 90 degrees; does that mean it shouldn't be used in hot weather at all, or just not actually applied to the leaves when the temp is above 90? Thanks in advance for any assistance. Rhonda Richmond, VA USDA Zone 7 I have one rose that occasionally gets powdery mildew and I tend to use the organic solution - baking soda. Check out the article at the American Rose Society for a variety of solutions: http://www.ars.org/About_Roses/disease_powdery1.htm I can't comment on the use of neem oil over 90 degrees, first because I've never used neem oil, second because it's hard to find daily temps *below* 90 degrees around here during the growing season! Gail near San Antonio TX Zone 8 Am I correct in assuming you make a baking soda solution in water? If so, what concentration are you using and are you spraying it directly on the leaves? Thanks so much for responding - I love this bush and I don't want to lose it the first year! Rhonda |
#4
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Treating powdery mildew in potted rose
"Natty Dread" wrote in message
... "Gail Futoran" wrote in message ... "Natty Dread" wrote in message .. . [cross-posted to rec.gardens] Hi all - I recently potted a new John F. Kennedy rose that is about 3.5 feet tall and has multiple canes with a few buds which are about to open. A lot of the leaves, especially at the top of the canes, are curling at the edges and have a white cast to them, which from my online research looks just like powdery mildew. What would be the best way to treat that in a potted rose? Should I remove all the infected leaves and cut back the canes, or try to treat it with fungicide first? It would be a shame to cut it back severely -- the bush has a nice upright shape and strong, healthy canes. Also, I read that neem oil shouldn't be applied when temps are over 90 degrees; does that mean it shouldn't be used in hot weather at all, or just not actually applied to the leaves when the temp is above 90? Thanks in advance for any assistance. Rhonda Richmond, VA USDA Zone 7 I have one rose that occasionally gets powdery mildew and I tend to use the organic solution - baking soda. Check out the article at the American Rose Society for a variety of solutions: http://www.ars.org/About_Roses/disease_powdery1.htm I can't comment on the use of neem oil over 90 degrees, first because I've never used neem oil, second because it's hard to find daily temps *below* 90 degrees around here during the growing season! Gail near San Antonio TX Zone 8 Am I correct in assuming you make a baking soda solution in water? If so, what concentration are you using and are you spraying it directly on the leaves? Thanks so much for responding - I love this bush and I don't want to lose it the first year! Rhonda I honestly can't remember what I did but the instructions at the ars site seem pretty specific: "Controlled experiments were conducted for some three years, using sodium bicarbonate or potassium bicarbonate in various combinations with insecticidal soap, Sunspray® ultra-fine spray oil, or only water. The result: both diseases were subdued by a weekly spraying of either sodium or potassium bicarbonate at 3 teaspoons per gallon of water, combined with Sunspray at 2 tablespoons per gallon of water. The bicarbonates eliminated the fungi, but addition of the Sunspray provided a spreader-sticker action that increased its performance." I've never used Sunspray. For sticking I tend to use Ivory liquid soap. Yep, the solution is to spray on the leaves. Moderation is the key. I hear what you're saying about loving the bush - I have a number of roses like that - but the John F Kennedy rose shouldn't be that hard to replace it. It's one of the hardest lessons I had to learn! Even now I have favorites that won't thrive in the ground, so I coddle them in pots. Gail near San Antonio TX Zone 8 |
#5
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Treating powdery mildew in potted rose
"jtill" wrote in message
oups.com... Gail Will this raise the pH in the pot above what the plant needs? Tha baking soda.Do I need to do something to avoid that? Joe T Baytown PS; The link you posted gave me the full story on PM for the first time. Thanks. Hi Joe - The nice thing about potted plants is that the water and excess minerals run out the bottom. I'd be more concerned about an excess of baking soda used on plants in the ground. There are some great sites out there for information. Several states and university ag departments also have good information. My bookmark file looks like the Library of Congress! LOL Gail near San Antonio TX Zone 8 |
#6
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Treating powdery mildew in potted rose
Hi Rhonda, to stop the powdery mildew from spreading you should remove
the infected leaves and cut back the stems, (not too severely - only just past where the mildew grows down to - which shouldn't be too far).....I know it's heartbreaking to do, but it does repeat flower, so you will still get your flowers -just a little later than you'd have prefered! and I'm sure you'd rather get rid of the spores now, to prevent any more spread of the disease. Also throw the diseased material in the garbage or burn it. The carb soda recipe should do the trick, I'll give you the recipe i have used with success at the rose garden i tend that has over 60 roses growing in it. 3 tspns bicarb, 1 and 1/2 tbspns vegetable oil and 1/2 tspn dishwashing liquid (the dishwashing liquid helps disperse the oil into the water) mix this with 1 gallon of water. and spray every 7 - 10 days on all the leaves and stems of the rose. Don't spray this during the hottest part of the day, and make sure you give the plant a good watering the day before you spray.(esp seeing it's in a pot) You may have to keep this up for 4-6 weeks or longer until the ideal environment for mildew to develop (ie warm days/cool nights/humidity) passes and the new spring growth "toughens up" and is not so susceptible. Also, next year, get in earlier with this spray, maybe early spring, to prevent it from re-occuring. Good luck with it, Elsie This is for Joe, the amount of bicarb being sprayed every 7-10 days isn't anywhere near enough to change the ph of the soil. Cheers |
#7
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Treating powdery mildew in potted rose
Thanks Elsie
Joe T |
#8
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Treating powdery mildew in potted rose
"jtill" wrote in message
ups.com... Thanks Elsie Joe T Agreed, that was a good post - well worth saving! Thanks to Elsie. Gail near San Antonio TX Zone 8 |
#9
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Treating powdery mildew in potted rose
Hey all, dropped by LOWE's , "YEAR AROUND DORMANT OIL" 11.98 per quart.
I checked contents. CANOLA OIL 98%, Inerts 2%. WOW! CANOLA is $2.50 qt. at Kroger. Joe T |
#10
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Treating powdery mildew in potted rose
"jtill" wrote in message
oups.com... Hey all, dropped by LOWE's , "YEAR AROUND DORMANT OIL" 11.98 per quart. I checked contents. CANOLA OIL 98%, Inerts 2%. WOW! CANOLA is $2.50 qt. at Kroger. Joe T LOL! And with the grocery store canola oil you can fry up and eat the rose blooms after you treat the leaves. Gail near San Antonio TX Zone 8 |
#11
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Treating powdery mildew in potted rose
jtill wrote: Hey all, dropped by LOWE's , "YEAR AROUND DORMANT OIL" 11.98 per quart. I checked contents. CANOLA OIL 98%, Inerts 2%. WOW! CANOLA is $2.50 qt. at Kroger. Joe T Hi Joe I haven't ever used Canola oil, only vegetable oil, so use your own judgement. And, yes, the price dif is amazing....why would you spend all that extra money on dormant oil, when vegetable oil (or canola, if you're going to use it) does the trick beautifully. ( I learnt this from an old gardener who had used veg oil instead of dormant oil on his plants with success for years.) I also make up my own white oil (pest oil) based on vegetable oil to combat scale on the roses. I have not had to buy dormant oil/pest oil for years. Much more economical - more money in our pockets to buy another rose plant! Happy gardening, Elsie |
#12
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I can't animadversion on the use of neem oil over 90 degrees, aboriginal because I've never used neem oil, additional because it's harder to find circadian temps 90 degrees around here during the growing season!
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