Allotments 4 All

Had a quick read.  If I were to put this into practice how could I do it?

For proven pumpkin help, says baking soda without oil is ineffective - what kind of oil could be used?  It wouldn't bind with the water anyhow without an emulsifier.

Or do I go for the spray for roses which uses 'a water solution of baking soda and insecticidal soap' - that I could do easily, but would it work on pumpkins?

If you have a decent local garden shop they may well have several oils in stock. However, in the UK they are mostly sold as organic pesticides rather than simply as neat oils. Virtually any plant/fish oil mixture sold as an organic plant pesticide or fungicide will do provided it is sold as a dilutable concentrate.

The one I know is VITAX Organic 2 in 1 which is sold as an organic insecticide, but you need to get the concentrate which you can dilute, and which contains its own emulsifiers.

If you prefer a neat oil, then NEEM is ideal

I also intended to mention, if you have powdery mildew on your tomatoes, then you might find the following of interest:-

http://www.ingentaconnect.com/content/bsc/jph/2003/00000151/00000003/art00005