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Winter care of roses with powdery mildew problems
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Posted by shadygarden_co z5 Denver (My Page) on Wed, Nov 26, 08 at 18:42
| My climbing roses -- two New Dawn and one Jeanne LaJoie -- have had lots of powdery mildew problems, as have some shrub roses. I have a book from the Denver Rose Society that says that for winter preparation on roses with mildew or blackspot problems, removing all leaves helps eliminate potential sites for harboring spores over winter. Gee, that seems like a lot of work, but I guess I could do it. I started doing it this afternoon, in fact, but it's going to take some time; in addition to which, I just had knee surgery a week ago and can't kneel.
My question is, first, do you all think that is important and necessary? And is it okay if you take out some of the branches or stems that the leaves are on? Second, I noticed what I think are mildew spores on the branches, kind of nestled next to the thorns and am wondering if I should just cut those branches off too.
Anyway, it said to do that as the first step in sanitizing and then to go ahead and spray for the mildew, which I have been spraying with the Cornell formula, Ultrafine oil and baking soda all summer, and will do again.
How do you all handle mildew problems? Last summer, the roses looked so beautiful early in the spring and then started getting the mildew and thrips, too, so I was spraying a lot. The second flush, I guess you would call it, was great for awhile, but I ended up with problems all summer and fall.
Any advice would be appreciated. Thanks in advance.
Marlene
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Follow-Up Postings:
RE: Winter care of roses with powdery mildew problems
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- Posted by hoovb z9 Southern CA (My Page) on
Wed, Nov 26, 08 at 19:16
| A dormant spray of lime-sulpher or copper might help more than Cornell. It would help the remaining foliage to drop as well as kill fungal spores. |
RE: Winter care of roses with powdery mildew problems
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| How do you all handle mildew problems? *** With a shovel. Life's too short to spend it growing disease-prone roses. I will give a rose some years to mature.
If it then continues troubled by mildew, I don't need it. New Dawn, in particular, is a mildew problem in my Southern California climate
(and generally not a good bloomer) -- so it is rarely grown here. Jeri |
RE: Winter care of roses with powdery mildew problems
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- Posted by elks US5, Can6b (My Page) on
Sat, Nov 29, 08 at 5:59
| This was a bad year for New Dawn in the Great Lakes area. During late summer and early autumn, we had many clear, cool nights, perfect for powdery mildew, and yes, the new tips took a beating, limiting the amount of rebloom. However, New Dawn is one of only a handful of remontant climbers that is reasonably hardy. I would be unwilling to part with it. In pruning it in late winter or early spring, take the laterals back to roughly 6" from their canes to promote new laterals to spring out next year. The infected tips can be cut back too, to remove any spores overwintering there as they are likely to do. Some people have found that a spray of 10% milk solution with a little liquid soap to act as a wetting agent controls powdery mildew. I do not spray. Steve. |
RE: Winter care of roses with powdery mildew problems
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| Powdery mild and thrips flourish in humid/moist environs. Look at your microclimate and assess the conditions. Try to control any factors, such as overhead watering, frequent watering, lack of good air circulation, etc., that lead to high humid/moist conditions. I have found that fungicides containing a sulfur compound work best. |
RE: Winter care of roses with powdery mildew problems
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- Posted by maryl Z7 Okla. (My Page) on
Sun, Nov 30, 08 at 19:44
| I've grown Jeanne La Joie for years and years and never had a powdery mildew problem with her. Blackspot definitely just not PM. Since PM is a definite problem on some of my roses I know that it's not just my climate. I suspect that the difference may be location. Jeanne La Joie is located along a fence in a windy site where air circulation is no problem. Also "dry feet" on a rose can help contribute to PM, so always make sure that your roses are well watered. As to picking off each and every leaf of roses prone to PM it sounds good, but most of us have a life. Your best offense is a good defense. For PM the Triflorene found in Ortho's Fungunex (sold now as Ortho's Rose Pride) gives very good protection against PM. But you must have it in place as soon as conditions are ripe and even before the leaves have fully leafed out. As soon as the day time temperature hits 68-70 degrees in spring start spraying per label instructions. Fungunex is also good for preventing blackspot if you have that. You might want to add a layer of bark mulch in early spring under the roses to cover up any leaves which may have fallen during winter and are harboring disease. Once PM strikes there really isn't any effective way to cure it. Preventative spraying will not return the affected leaves back to looking good, but will prevent new infection. Now you can spray with any material you like. But if it isn't doing the job then what's the point. I used the Cornell forumla years before and it not only wasn't effective on some of my roses, it actually harmed others. But then we have a long growing season with lots of time for disease to take hold....As for Thrips, I've found nothing effective against them that I didn't consider too toxic. They are cyclical, so some years are worse then others. Personally I've gotten rid of those roses that suffered severe Thrips damage every year and just live with the occasional damage on my other roses. |
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