Blackfly on my beans

There are some organic pesticides that can be used, such as pyrethrin. You could probably google them.

A lot of people use dilute washing up liquid but make sure you don't use it at times of the day when bees and ladybirds are around - although, if the ladybirds are around, you wouldn't have the blackfly problem. Ladybirds tend not to start working on the blackfly until they are in sufficient concentration to make it worth their while

A Neem oil dilution is also supposed to work well. As is a mixture made by soaking hot chillies in water (be sure to strain the water before spraying and wear a mask or cloth over your nose and mouth). Both of these need to be used at the right time of day as well as they are contact killers.

There are some commercial killers such as BugClear etc.

If there is not too much to do you could wash them off by hand or hose.