Thank you very much for the explanation.

Any "modification" adding vinegar appears to be counter productive as the acid (vinegar) will just react with the base (baking soda) leaving a more dilute solution of which ever was added in excess.

From Mike Mcgrath at WHYY website;
The Cornell Formula.
 In one gallon of water, mix and repeatedly shake:
 1 tablespoon baking soda
 2 drops dishwashing liquid or insecticidal soap
 1 tablespoon oil. You can use vegetable oil, but Âhorticultural oil will work better, especially one of the new lighter-weight "summer oils". (Cowboy Gardeners: Do NOT use motor oil or WD-40 or any other such foolish thing.)

I found an interesting article today on Yahoo news regarding the Cornell Formula. It kind of explains how it orginated. It seems that horticultural oil was dismissed early on in the research done at Cornell because of some "negative characteristics". It does not say what those were though.

Here is a link that might be useful: Cornell Formula article on yahoo

what is the Cornell formula used for? Is it eradication of bugs?

Joy

Joy, it is used as a fungicide.

The original Cornell Formula is now a commercial product. Here is the link for the original Cornell Formula.

Sengyan

http://www.hiagritech.com/pressreleases.htm

If you want to grow HT Roses and Climbers,one must spray! This formula is for mildew,but what about aphids,blackspot and rose slugs(midges)? I incorporate Safer's BTK or equivalent, (a natural Insecticide against midges-the green grubs which will eat your roses to the ground))into this spray along with some dish soap, and a little bit of horticultural sulphur, and cover all bases with one spray! The best I know of that works.

I thought this formula was for both insects, mildew and black spot. I've started using it for black spot so I hope so! I would think the hort oil takes care of the insects as well, no?