Whitefly

I seem to have quite the invasion of whitefly - it's not something I remember from last year, certainly not on the courgettes, but this year they are trying to make a home on the broccoli and courgettes. And sadly they are firmly established on all four citrus trees. I've been spraying (more like drenching both sides of all the leaves!) Neem oil every three days (they've just had their third cycle of that regime), which seems to be working on the broccoli and courgetes as there's nothing on them today and no sign of any eggs. I think I might still have a battle on my hands over the citrus though.