Whitefly parasites (for control of whiteflies)
Tiny whitefly parasites (Encarsia formosa) lay their eggs inside developing whitefly pupa, so one of their babies hatches out instead of the whitefly! So small their flights are measured in inches, not feet, you'11 probably not even see whitefly parasites (except with magnification), but they spell death for whiteflies.

For fastest control, make 4 releases of parasites, spaced 2 weeks apart for greenhouse whitefly. If you have sweet-potato whitefly (page 5), continue with releases every 2 weeks until control is reached. 1000 whitefly parasites is enough for a 1000 square foot greenhouse with a low-level infestation (a few whiteflies per plant).

Encarsa formosa come packaged ready to hatch, glued to small cards. The perforated cards are hung from plant foliage, and parasites emerge as adults within 2 weeks. Then they fly off, and begin looking for more whitefly pupae to parasitize.

Since they're so tiny, how do you know they're working? With greenhouse whitefly, within 10 days the parasitized pupa turns totally jet-black in color, instead of its normal clearish- green color. With sweet-potato whitefly the pupa turns only slightly yellowish, but after 2 or 3 weeks the "emergence hole" can be seen in both cases when the adult parasite chews his way out (16X magnifier required).

Parasites work best when temperatures average at least 68'F. (add daytime ~ nighttime temperatures, divide by 2), Lower temperatures than these will require more frequent releases, at least monthly.