I bought the short course of two deliveries of parasitic encarsia wasp for my greenhouse whitefly problem. They arrived promptly, just as described and are good value when compared to other companies online offerings. The wasps have hatched and I know they must be settling in as I've seen the parasitised whitefly larvae. I trust they'll keep the pest problem small this year. I don't think anyone can expect total eradication of the whitefly but tiny numbers won't be a problem. This is a great way to do it without horrid chemicals. I recommend "green gardener". Do try them.