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Ninebark and powdery mildew


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#1 Lee

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Posted 26 April 2012 - 08:52 AM

Has anyone else had problems with mildew on their Ninebark? For the past two years I have found it in early spring on both Coppertina and Diablo. If not treated, it covers the whole plant. I have "googled" and found that this seems to be a common problem with this shrub in other areas of the country. Does anyone have any suggestions on treating the mildew organically? I have cut my plants to about a foot high, hoping to get as much mildew off as possible. I love these shrubs, but am about ready to pull them if it entails constant fussing and spraying to save them.

#2 Guest_dcsmith796_*

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Posted 26 April 2012 - 09:32 AM

How tight are the stems at a foot tall? If they're tight and the shortening doesn't fix it, and if you're willing to give them one more year, you might try thinning, rather than shortening, to increase airflow and keep the leaves a little drier in the spring.

If they're subjected to irrigation spray, you might check to see if modifying the watering schedule could dry them out a little quicker.

If none of those things works, then I'm with you - move 'em or lose 'em.

#3 Cricket

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Posted 26 April 2012 - 06:32 PM

Are the ninebark sited in a sunny spot? To much shade or shade in the afternoon can contribute to mildew...

A good rule of thumb when pruning out canes: Remove up to a 1/3 of older canes a year...

Consider donating your shrubs to a volunteer garden group should you decide not to keep them...

#4 Lee

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Posted 28 April 2012 - 09:37 AM

Thank you both for good ideas on dealing with this. The plants are in full sun, not subject to sprinklers, and in sandy loam. I will try thinning the interior of the plant, but it will still leave me with affected branches. I read about a milk and water spray for fungus--has anyone tried this?

#5 Janet Macunovich

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Posted 28 April 2012 - 08:02 PM

Ah. Are they running dry, then? Stressed plants get mildew -- for instance, bee balm is more prone to mildew when it's grown dry.

Interesting article with a University of Connecticut evaluation of various ninebarks for mildew resistance, at http://www.amerinurs...ticle-7868.aspx -- note that Summer Wine is pretty good but plain old, been-around- forevere' Nanus' is a virtual star.

Also notes there about you-didn't-suspect-this-is-what-mildew-can-do fungal deformities.

As for treating mildew-prone plants:
Milk and water I haven't heard of, but Cornell University Extension did quite a lot with baking soda and water years back; found it fairly effective, although it had to be re-applied after rains and in general applied more often than over-the-counter fungicides (which are formulated with sticking agents in the mix). MY daughter an I used it on roses and phlox and tried to be scientific about it -- it was helpful against mildew and black spot but no way was it armor-all, or a cure.

The garlic oils, oil soap sprays (we've used Murphy's oil soap, 1T in about half-gallon of water) and even canola oil, have shown as much effect in mildew prevention. (None of the fungicides or home formulae are curatives, just preventives.) Also the anti-dessicants form effective fungus-protection barriers -- products such as Wilt Pruf and Moistur-in.

But just to say: Organic is a slippery term. How natural is it for a plant to have a milk bath, or for stems and soil to be doused with sodium bicarb or oil? All organic tenets say to first make sure you have done everything you can to correct the culture -- the light, air, water, soil -- before doing these things with topicals.


#6 Lee

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Posted 01 May 2012 - 11:31 AM

Janet-Thanks so much for the very informative link. I do have the witch brooming that they talked about in the article, and deformity of leaves and branches. I have never heard that stressed plants can be susceptable to mildew--thought it only occurred with excess moisture. You are right that the "organic" solutions should be secondary to culture. I think that I will have to re-think these plants in my landscape, as much as I like them.




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