Blackfly - if and when and how to treat?

[cazp]

My beans have quite a few black fly particularly on the top leaves. There are a few ladybirds doing their bit for me and I did read in a book that blackfly are harmless unless in large numbers.

So what would be considered a large number of blackfly?, and what is the best (least chemical) way of treating them? if at all.

I was hosing the leaves with water but now don't want to disturb the ladybirds!

Any advice appreciated thanks...

[Two_Sheds]

Squish with your fingers

[cazp]

Thanks for your advice!! that will be my task tomorrow.....