See:
http://forums2.gardenweb.com/forums/load/roses/msg030010308429.html

AND

http://forums2.gardenweb.com/forums/load/roses/msg1120282813822.html

Here is a link that might be useful: link to first thread above

Thanks for the links.
Nik

Most of the references I can find discuss root application (hydroponics or soil drenching). I wonder if foliar applications can be effective and if they might have some negative effect by limiting the ability of the leaf to perform its functions.

Will do a little testing and report back although a minimally scientific test will have to wait until next year when I will be able to obtain from the same source multiple copies of a rose known to mildew badly in my garden (Duchesse de Brabant springs to mind).

The concoction I have in hand is very alkaline (pH > 9) even when diluted at the recommended rate and I wonder if this property might just have some effect regardless of the silica content. The same might apply to the potassium carbonate that is bound with the silicon oxide.
Nik

This is a research leaf application paper.

http://hortsci.ashspublications.org/content/35/4/773.full.pdf

Here is a link that might be useful: link for above