Jim: What little I know about dormant oil sprays says that they are highly refined to exacting standards. If you make something of your own, I think you risk damaging your plants.

The Fruitnut

Jim:

I have heard of people using canola oil (rapeseed) as a substitute for dormant oil, but I would't do that myself. As the fruitnut observes, agricultural dormant oils are specifically formulated and refined for that purpose. Why would you want to mix something up at home, which might be of dubious effect and safety, when dormant oils are fairly cheap (when purchased in quantity), and of proven effectiveness?

Don Yellman, Great Falls, VA

I am from the old continent of Europe and I grew in my family farms.In the old days most of the sprays used on orchards, farms and vineyards were mixed by the workers.I never heard of any wrong mixing or cathastrophic mistake.The workers superintendent always made sure trained workers prepared the concoctions. In those days the components of the mixtures were baught in agricultural supply stores and things were not mass produced as a mixture. This was done in small to large farms.It just did not require to be a chemist to mix those basic sprays. Just follow basic instructions and safety precautions.Of course these were simple but effective formulations. Nothing like DDT's and other complex mixtures that exist today.
Another question is how much dormant oil do you have to buy in order to have it cheap?Only large commercial orchardists have access to that type of prices because they use it in large scale.They buy from commercial suppliers that do not sell to the public or domestic user. Anyway I appreciate your comments.Jaime

I buy my dormant oil from a local farm supply. It is sold in two and one half gallon containers,it is derived from a paraffin base and is not expensive. Al

I doubt that many of us have ready access to strong but harmless emulsifiers to get any oil to go into suspension in water.
Were oil sprays, say 80 years ago, simply oil and not oil and water?