If you're certain its Thrips, then you need to spray with a pesticide which is approved for use on food plants and which treats for thrips. Not sure of any names of sprays though, you'd need to check the bottles for information.

Not too many of those in the UK, Bamboo. I would use spinosad--carefully, to avoid bees--but I don't think that that is approved there. I would double check the diagnosis, though, Pat. Thrips eat the skin off the young leaves before they expand, causing distortion, but not much loss of efficiency. Normally they aren't much of a problem unless they atack the young pods.

I've only ever seen thrips on peas, not on beans.