Thought I'd share this article from Dave's Garden.

http://davesgarden.com/guides/articles/view/3610/

Apparently what used to be called "dormant spray/oil" is now
formulated quite differently. Inter alia, it is no longer necessarily
petroleum-based. Article says it can be used on Whitefly. NOW they
tell me! I had such horrible struggles with Whitefly on my Hibiscus--
tried everything! -- that I finally got rid of it some years ago.

Hope article is of interest to others.

HB