Thank you, Henry, for informing us. I read the link, it's great. I have powdery mildew on my peonies (in the fall when the sun is lowest, and my tall house shade them) - I wonder where you get silicon from. Is it in some soil, or we can buy it? Thank you.

Strawberry, the source of silicon in the article is potassium silicate. This stuff is available from several sources, mainly for hydroponic use (the claim is that the silicates strengthen plant tissue). If you want to try it, a good source might be Planet Natural's Pro Silicate. It's relatively cheap and comes with instructions for both hydroponic and normal soil-application gardening.

Here is a link that might be useful: Pro Silicate

That was interesting Henry, thank you.

I know silica plays a part in plant growth and development, but I question what effects it may have on edibles and US when consumed. Probably not an issue for "garden roses", but for those who grow edibles around their roses or close enough where sprays or applications could drift or wash into root zones it may be. I realize the hydroponic sources state they are for "vegetable growing". Here in the Los Angeles area, there are MANY hydroponic stores and it's obvious VERY few are growing "cash crops" like tomatoes! Kim

Considering there are 454 grams per pound it is "DIRT CHEAP" LOL

Potassium Silicate one pound, 32% K2O 52.8% SiO2

One pound costs $12.00 = 648 gallons of product at 98 PPM

.7 grams in one gallon of water yields 98ppm SiO2 or 46ppm Si, and 49ppm K.

Soluble Silicon; For Crop and Disease Management of Greenhouse Crops

ALTHOUGH THE PRODUCT MSDS says it is irritating to skin, eyes and lungs so it may be somewhat difficult to use safely

Here is a link that might be useful: Online seller of potassium metasilicate

I would not recommend spraying because of possible lung problems. It is my understanding that the Si compounds in water solution are added to the soil to be absorbed by the roots.

There are a few people reporting success with corn-meal dusting for mildew on roses. I tried that last year on Wise Portia in 2 hours of sunlight in late fall - she got only 3 mildewed leaves, that's pretty good for her mildew-prone reputation. I'll move Wise Portia to get full sun, but will try corn-meal dusting on partial shade peonies in late fall for experimental purpose.

Sounds like it may help some with blackspot.

Here is a link that might be useful: blackspot research

I wonder if the silicon compound concentrations would discourage Japanese Beetles and/or the mite that causes rose rosette virus and/or the aphids that spread rose spring dwarf virus.

"004 Root Application of Potassium Silicate Reduce Feeding Damage to Sargent Crabapple Leaf Tissues by Adult Japanese Beetles" (see link below)
There also is a 2001 report by A. M. Shirzai and F. D. Miller in the following:

Shirazi A.M. and F.D. Miller 2001. Root application of potassium silicate reduce feeding damage to Sargent crabapple leaf tissues by adult Japanese beetles. p. 390. Poster Abstracts. In L.E. Datnoff et al., (eds.) Studies in Plant Science: Silicon in Agriculture Vol. 8, Elsevier Science. B.V., Amsterdam.

Here is a link that might be useful: Shirazi and Miller link HortScience June 1999 vol. 34 no. 3 441

I wonder if adding a silicate to the rose's water will "encourage" the rose rosette virus carrying mites to go elsewhere.
"The most widely accepted mechanism for the action of silicon in increasing plant resistance to insect attack is reduced digestibility and increased hardness and abrasiveness of plant tissues due to silica deposition, mainly as opaline phytoliths, in various tissues, including ... " a quote from the following full paper:

http://onlinelibrary.wiley.com/doi/10.1111/j.1461-9563.2009.00430.x/abstract?userIsAuthenticated=false&deniedAccessCustomisedMessage=
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Silicon use for pest control in agriculture: a review.

http://www.cabdirect.org/abstracts/20063156274.html
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Utilization of Silica to Suppress Populations of the Cotton Leafworm, Spodoptera littoralis Boisd. on SugarBeet

http://scholar.googleusercontent.com/scholar?q=cache:S3tJZObU58AJ:scholar.google.com/&hl=en&as_sdt=5,36&sciodt=0,36
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Silicon as a plant defence against insect herbivory: response to Massey, Ennos and Hartley

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2656.2008.01380.x/full
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Larval performance of the pyralid borer Eldana saccharina Walker and stalk damage in sugarcane: Influence of plant silicon, cultivar and feeding site

http://www.ingentaconnect.com/content/tandf/ttpm/2007/00000053/00000003/art00002
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EFFECT OF CALCIUM SILICATE ON FEEDING AND DEVELOPMENT OF TROPICAL SOD WEBWORMS (LEPIDOPTERA: PYRALIDAE)

http://www.bioone.org/doi/pdf/10.1653/0015-40402004087%5B0393%3AEOCSOF%5D2.0.CO%3B2
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Feeding non-preference of the corn leaf aphid Rhopalosiphum maidis (Fitch, 1856) (Hemiptera: Aphididae) to corn plants (Zea mays L.) treated with silicon

http://www.scielo.br/scielo.php?pid=S1413-70542005000400007&script=sci_arttext
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Prospective of Silicon fertilization for citrus in Florida.

http://www.cabdirect.org/abstracts/20013019206.html;jsessionid=FA38EF269620FDCFD8A2C29C606204AC
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Even rabbilts do not like silicon in leaves. See link below as it is too long to post here.

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Combination of silicate and biocontrol of two spotted spider mite

http://www.tandfonline.com/doi/abs/10.1080/09670874.2010.495794

Here is a link that might be useful: rabbits and silicon

Abstract for very recent review (you probably could see the full paper in a large university library).

I have the full paper. Under current law I can e-mail a limited number of copies for educational purposes. Below is a quote for the main example for roses in the full review:

"Similarly, recent research on the beneficial effect of silicon in roses clearly shows that the heightened resistance against Podosphaera pannosa is the result of an increased formation of papillae and deposition of callose and H2O2, along with an upregulation of the phenylpropanoid pathway producing antimicrobial phenolic compounds and flavonoids (Shetty et al., 2011,2012)."

They cited the following two papers:

Authors: Shetty R, Frette X, Jensen B, Shetty NP, Jensen JD, Jorgensen HJL, Newman MA, Christensen LP.

Title: Silicon-induced changes in antifungal phenolic acids, flavonoids, and key phenylpropanoid pathway genes during the interaction between miniature roses and the biotrophic pathogen Podosphaera pannosa.

Published in: Plant Physiology 157, 2194�2205, (2011).
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Authors: Shetty R, Jensen B, Shetty NP, Hansen M, Hansen CW, Starkey KR, Jorgensen HJL.

Title: Silicon induced resistance against powdery mildew of roses caused by Podosphaera pannosa.

Published in: Plant Pathology 61, 120�131, (2012).

Here is a link that might be useful: very recent review