This predator is very similar to Encarsis but useful for a slightly different kind of whitefly. If you find encarsia is not as effective as expected then it is possible that your whitefly is not the usual glasshouse whitefly.
Eretmocerus is used exactly like Encarsia, except that the predator is a gold colour and when the whitefly scales are parasited they turn gold, so they are not so easy to spot as the encarsia parasites. It works best from April to August, but is less sensitive to the higher temperatures of midsummer - so if your greenhouse is getting above 30 degrees in midsummer then choose eretmocerus rather than encarsia. Most commercial growere use both predators.
The Standard pack (5 cards) should give good control for an average conservatory or small greenhouse. If you have a longstanding battle with whitefly order two packs with separate delivery dates. Then you can follow up the initial treatment with a second introduction two weeks later. The Larger pack should be used if the Whitefly infestation is very bad or the area large.
More technical information
Glasshouse whitefly have wings which form a heart-shape when viewed from above (see photo on left). Tobacco whitefly have parallel wings which are longer, and when folded you can still see a strip of their back between the wings. (see photo on right)For information to help you identify your whitefly Click here for DEFRA information sheet