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Powdery mildew
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Posted by
vignewood z6 CT (
My Page) on
Sun, Jun 26, 11 at 23:02
| Last year I planted two shrub roses that developed powdery mildew. I tried several products to get rid of it. This year they again developed powdery mildew. I tried a solution of water, vinegar, oil, and baking soda and it seemed to help but burned the tips of the leaves. Now the mildew is starting to appear again. Should I shovel prune them? All my other roses are doing extremely well. |
Follow-Up Postings:
RE: Powdery mildew
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| The bicarbonate ion in baking soda can provide reasonable control of rose mildew if used properly. The link below gives a good description of bicarbonate-based fungicides. I suspect the best product for rose mildew is potassium bicarbonate as found in Kaligree, Amicarb, or Remedy. I would make two other generalizations: 1) Avoid anything called the Cornell formula. No one at Cornell invented or studied such a product. 2) Avoid any product containing both vinegar and baking soda. Mixing these two compounds negates any fungicidal properties of either component and is just plain silly. |
Here is a link that might be useful: Bicarbonate fungicides
RE: Powdery mildew
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| I found that article very helpful and interesting and it led me to do some more Googling about Potassium Bicarbonate. Here is some follow-up that I thought worthy: Susan |
Here is a link that might be useful: more about Potassium Bicarbonate
RE: Powdery mildew
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| sp. Kaligreen and Armicarb. ;) Otherwise you can trust advice from mike_rivers. |
RE: Powdery mildew
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| Thanks Mike. Are those products a cure or just a temporary fix? If I am going to continually have to put chemicals on these roses I may just replace them with some that are mildew resistant. I think Sweet Drift Roses are prone to disease even though they boast that they are exceptionally disease resistant. What do you think? I have a shrub 10 feet away that has never had a problem. |
RE: Powdery mildew
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| Potassium bicarbonate is reported to kill existing infections and prevent future infections - when applied on a regular basis. In a controlled test at Texas A&M, reported in F&N Tests in 1999, weekly applications of Kaligreen gave "acceptable" control of powdery mildew on miniature roses. Actually, the results were quite similar to those obtained with weekly applications of Banner Maxx. In my part of central Michigan, powdery mildew on roses is very rare and my experience is mostly with phlox mildew. I obtained good control with my own mix of oil and potassium bicarbonate but I eventually found mildew-resistant phlox varieties and growing these has been a whole lot more enjoyable. I would check around and see if rose mildew is common in your area. If it is not, I would probably replace your two shrubs. |
RE: Powdery mildew
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- Posted by seil z6 MI (My Page) on
Mon, Jun 27, 11 at 21:12
| I would also avoid any recipe that calls for any kind of oil. Between the vinegar and the oil you probably cooked your leaves. I used a similar recipe once too and had severe leaf burn as a result. I have used a home brew that has baking soda, powdered milk and a few drops of dish soap (the soap acts like a sticker/spreader and you only need a drop or two) that did OK and did not burn my leaves. |
RE: Powdery mildew
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| Seil - what part is the powdered milk supposed to play? I did use the baking soda, drops of dish soap and mineral oil this past winter and very early spring, and it worked great. I was forewarned to leave the oil out in the heat. |
RE: Powdery mildew
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| Milk is said to promote the growth of beneficial bacteria that eat the mildew. Careful with these recipes where some gardener has thrown together everything he ever heard of. They may be harmful or ineffective. It is usually quite easy to knock down a mildew infection with a single ingredient such as bicarbonate or oil or sulfur or antitranspirant etc. Is it a "cure"? Of the current infection, perhaps, but the disease is spread by airborne spores that can travel great distances. Also, in one stage of the life cycle, mildew can overwinter in dormant growth buds. However, in most locations except for the Pacific coast, mildew is intermittent or even uncommon, so that preventative spraying is not needed. It requires very specific conditions (cool night temperatures with high humidity and no rain). |
RE: Powdery mildew
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- Posted by hollyr 5 - Southwest Ohio (My Page) on
Thu, Jun 30, 11 at 16:10
| Got Jerry Baker's book on home remedies and concoctions to use in the garden. He said to use 3c water; 2T baby shampoo; 2T hydrogen peroxide; 1t instant tea for powdery mildew and spray it once a week on roses that were prone and I also have used it on my bee balm and phlox. No mildew so for this year - and we've had an extremely wet spring and start to summer. |
RE: Powdery mildew
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| Sorry, but Jerry Baker's methods are all a crock. You're lucky if any of them work without destroying a rose. His formulas usually contain enough nutrients and organics that it won't kill a healthy plant and when things stay the same or luckily get a little better, everyone thinks the formula is a miracle. Try it on some sensitive roses that are prone to leaf burn or other nutrient sensitivity and you could end up with a dead rose. Stick to experienced Consulting Rosarians' recommendations, ARS, your local rose society, or some of the more trustworthy members here on this forum, instead. |
RE: Powdery mildew
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- Posted by seil z6 MI (My Page) on
Thu, Jun 30, 11 at 22:05
| Good info, Michaelg. I also think the milk is supposed to leave a coating on the leaves to prevent re-infection. I have to agree, rosetom, Jerry Baker's recipes have never worked for me. I think it's mostly hype. |
RE: Powdery mildew
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| I'm also in 6b CT and powdery mildew is virtually nonexistant even with all the rain we occasionally have. I spray with BannerMaxx which is absolutely necessary for BS and handles PM as well. If you don't spray I think that you will find BS to be the far greater problem. |
RE: Powdery mildew
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| I live in Wenatchee WA and since it turned to much hotter days my roses have gotten powdery mildew. Not all but it seems to be spreading. Could anybody suggest a recipe for a spray using the potassium bicarbonate? I would greatly appreciate it. :-) |
RE: Powdery mildew
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Water.
Easiest solution. Every morning go out and spritz your leaves. Powdery mildew needs dry leaves in order to survive. If you do this from the start you won't have to deal with pm ever. With an already infected plant, it won't cure the pm. But it will stop it from spreading. |
RE: Powdery mildew
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Water.
Easiest solution. Every morning go out and spritz your leaves. Powdery mildew needs dry leaves in order to survive. If you do this from the start you won't have to deal with pm ever. With an already infected plant, it won't cure the pm. But it will stop it from spreading. |
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