Worm castings are good! But, probably not THAT good. As a teenager, I discovered the positive aspects of verniculture as an adjunct to raising and selling earthworms to local fishermen as bait. Worm castings are really good for plants. But as an insect repellent? I remain unconvinced as yet, but am willing to learn. BTW, for a different look at the subject from that espoused by those hoping to make $ from it, see
http://www.bonniewren.com/castings.html .
In the meantime, as one who has battled whiteflies of several types over half a century, I can tell you what REALLY works. Unfortunately, because of the evolutionary process known as "natural selection" postulated by Charles Darwin, in his treatise "Origin of the Specie and the Descent of Man", almost anything that results in killing off hordes of any pest, leaves those few that are resistant to the method to propagate the next generation, many of which may inherit resistance. This even can work with flypaper. Probably also with worm castings, should they be effective at all. Flies that dislike landing on vertical sticky stuff survive to propagate the next generation.
So, what can one do about whiteflies right now? As with any thing that works, be advised that it is best to use the method with restraint, and switch tactics from year to year to keep the little buggers confused.
Use everything you already know about (Safer soap, worm castings, yellow sticky traps, thiodan, predatory insects, parasites, and pathogenic fungi.), and then, to enjoy the rare whitefly free season, employ the nuclear bomb of whitefly control: Imidacloprid. Admire 2e (listed for food crops with specific application instructions) and Marathon (listed only for non-food applications) can produce a whitefly free season for you. As noted above, you should avoid using these chemicals year after year as resistance will occur. As with any chemical, follow the label explicitly, as these chemicals are highly toxic (they are developed from nicotine).
If you recoil from using such dangerous chemicals, think about what you do with sodiun hypochlorite every week. Clorox! Or Draino. Try mixing the two together. Be sure your medical insurance is paid up beforehand. Or spill some brake fluid in a container of swimming pool chlorine. Before you do that, be sure to arrange for a prepaid funeral.
Actuallly, the whole of American culture has become a society of wimps regarding chemicals. If you don't believe that, look up the most common greenhouse fumigant used in 1945. It was hydrogen cyanide, the same chemical used in execution gas chambers.
Oh!, for the good old days!...
