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Broad beans - great!  Coming along well. 2 days later - all the plants are covered with blackfly. Also the small beans down the plants. What do I do? Nip off the tops? The pests are allover the whole plant. I have chopped off most at the base and hope they sprout again. Others on the site have the same problem. In Denmark so not the same as UK perhaps. I threw the affected plants in a dalek compost bin. Mistake? HELP.

I spray them off with diluted washing up liquid - about twice as strong as you use for washing dishes. I think it drowns them rather than acting as an insecticide and is therefore okay to mention on here?

Personally I wouldn't use washing up liquid as it is a chemical detergent and more like to damage plant material than a proper "natural" soap - the general advice is to wash the plants after an hour or so if you use detergent based sprays.  Insects are killed on contact (with either spray) so they really are an insecticidal in action - they are a contact killer - the fatty acids interfere with cell membranes and essentially the insects leak to death!

I make my own soap and use that but you can also mix it with neem oil or use any other repellent like garlic or rhubarb...

a good stream of water from a sprayer will wash most off or squish them by hand or use insecticidal soft soap. I used the soap first and took off the top couple of inches on every plant. Next day I used a water spray on those that were left. Day after that I squished. In the meantime I fed the plants as they were looking browbeaten and I put diatomaceous earth at the base to get rid of the ants which were farming the blackfly. They look great now and have fully recovered, the infestation took a lot out of them

Thanks for your advice.  But now I have found blackfly on the underside of leaf beet!  I begin to think we have a plague.  I thought leaf beet never suffered from anything at all!

you need nasturtiums to attract the blackfly away, also companion plants like poached egg plants to attract predators

What variety are they? I find that some are very susceptible; I grew Grando Violetto once, and it was eaten alive, but only a few plants of Aquadulce get infested. Those that are carry on as though the things weren't there.