I am going to experiment with Diatomaceous Earth and Boric acid powder to make my own powdered insecticide. The mixture will be 20 to 1 Diatomaceous earth to Boric acid powder. Proportions picked as a reasonable practical experiment. The diatomacious earth is primarily to bulk out the boric acid.
My reasoning goes like this:
Diatomaceous earth is not regarded an insecticide,since there has been little to no research done, and the so called supporting evidence is anecdotal.
Boric acid is harmful to many insects which are similar to those encountered in the garden, and this is well documented.
Powders are often irritating to insects. Wood ash for example simply because it makes their inhabitant uncomfortable, hence they tend to move on.
So my home made insecticide will have some poison, some anecdotal support from the diatomaceous earth, and also the powder effect. This cannot possibly be more harmful than many of the commercial products sold for insect control.
Bugs that cause damage to my plants are the ubiquitous flea beetle, Cabbage butterfly, Japanese beetle, and Colorado potato beetle. Reducing the effects of the first two would be a great plus.
Dispensing will be by using my recently purchased Duster.http://www.durgan.org/URL/?FCWDO
6 January 2012 Garden Dust Sprayer.