Smoke bomb! How to get rid of Greenfly and Whitefly in a polytunnel and greenhouse

I've got a problem with greenfly and whitefly in my greenhouse and polytunnel. I have sprayed everything a couple of times now which seems to reduce the numbers, but a week or so later there back in damaging quantities. I'm assuming they are not getting sprayed as they are under the leaves, and I've got too many plants to individually spray every leaf underside. I remember my dad using greenhouse bombs years ago, which you light with a match close the door and they filled the greenhouse with smoke, and a pesticide that eradicated the problem. I can only assume that have been outlawed due to environmental concerns, can anyone recommend a good treatment that will fumigate the inside and hopefully rid me of the problem. The plants I need to treat are herbs, veggies, and summer bedding, with the fuchsia's and herbs worst effected, although some of my peas and beans are starting to look poorly now as well.