Blackfly

Anyone got any remedies for blackfly on dahlias and beans.  I'm resorting to squishing. The ants are having a lovely time farming them. I'm thinking of sprinkling some semolina on the ground beneath the plants, supposedly the ants take it as food and when it gets eaten it swells in their tummies.  I'm not sure I believe it but if the ants aren't farming it might reduce the blackfly. Then again at least the ants put the blackfly all on one place ready for squishing   so I might be making matters worse.

I tend to leave black fly on my broad beans they tend not to affect the crop so I leave em to it. Can't help re dahlias I'm afraid.

Squirt them off with a hose, or spray with soapy water. Check for hoverfly and ladybird eggs though, if they've arrived the blackfly will be gobbled up in no time. We've got loads of blackfly on the nasturtiums but the hoverfly larvae are seeing them off.

There's a great dearth of ladybirds, their larvae or eggs around here and I've never noticed hoverfly larvae, the only thing around the blackfly are ants.

This year, after years of squirting with savon noir or squishing by hand, I just ignored the ones on the broad beans and after about ten days or so they'd been largely consumed. We did have a lot of ladybirds already in place, but also found hoverflies moving in and laying eggs. Black caps and tits had their share, too. No idea if I was just lucky this year, or previously I've been squirting/squishing the predators as well. But saying that, we don't have lots of ants - some, but not huge numbers.
There are some on the french beans this year, but none on the dahlias.
I tried putting jam down one year, the idea that after a really sugary feed the ants prefer meat to the honeydew the aphids produce, but it didn't work!
Sorry, not much help

I ignored them on the broad beans this year and they ruined the crop. I've left myself notes to remember to pinch out the tops early next year. Having had a wonderful time on the B Beans they're now holidaying on the CFB and DFB. They're out to get me

I had some on broadbeans and removed the worst (snapped off the stems about where they were down to). kept an eye on them. There were a couple of spots building up again 2 days later so I repeated and that dealt with them. don't know if you could do the same with dahlias.