On Sun, 19 Aug 2007 21:11:10 +1200, "George.com"
wrote:


baking soda in a bit of oil also does the same job apparently.
http://www.ghorganics.com/page15.html#Milk for Mildew:
Baking Soda Spray
For anthracnose, early tomato blight, leaf blight and spots, powdery mildew,
and as a general fungicide
Sodium bicarbonate commonly known as baking soda has been found to posses
fungicidal properties. It is recommended for plants that already have
powdery mildew to hose down all the infected leaves prior to treatment. This
helps to dislodge as many of the spores as possibly to help you get better
results. Use as a prevention or as treatment at first signs of any of the
diseases.
To make: Mix 1 tablespoon baking soda, 2 1/2 tablespoons vegetable oil with
one gallon of water. Shake this up very thoroughly. To this mix add 1/2
teaspoon of pure Castile soap and spray. Be sure to agitate your sprayer
while you work to keep the ingredients from separating. Cover upper and
lower leaf surfaces and spray some on the soil. Repeat every 5-7 days as
needed.

I would question whether it's the baking soda or the oil that has the
fungicidal properties, or even the soap, otherwise why not just use
baking soda on its own. It looks to me as though the baking soda (a
mild alkali) and the soap are there to help stabilise the oil
emulsion. It would also need very energetic shaking to get a good
emulsion. A paint stirrer on an electric drill, or a food blender,
might be better than shaking. The better the emulsion, the more
effective the spray.

I would also expect the mix to be quite good as an insecticide.
Several of these on the market nowadays are little more than emulsions
of vegetable oil in water, stabilised with a soap of some sort, and
best not used indoors.


--
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net