[BabyStar]

My top-performing vegetables, the broad beans, are getting infested with black aphids. I don't like using chemicals and try to stay as organic as possible (plus I think it's too late to spray them with anything now they're fruiting?), I spray them off with a good spray of water.
Are they actually harmful to the plants? I'm trying to keep numbers down so not seeing any noticeable damage but they are mighty annoying!

[BabbyAnn]

any aphid (black, green, white(fly)) is a sucking pest and multiplies at a phenomenal rate, not to mention excrete a honeydew which goes mouldy ... the risk of disease and plant collapse are high, not to mention a reduced crop.

You don't need to use chemicals - nip off the growing tip as this is the tender part of the plants where aphids always go.  Dilute washing up liquid is a very good alternate to pesticide (use a spray or watering can, or as my mother used to do, tip the (cooled) washing up water from the breakfast things over the plants in a deluge)  Spraying them off as you have is also a good idea.

[savbo]

I've done broad beans for a few years now, always get loads of black aphids, even when I remember to pinch out the tip to discourage them - and have always had an abundant crop.

sav

[sunshineband]

We seem to avoid these

Not sure if the large number of blue tits and robin babies are responsible

[OpenSourceAgriculture]

No, don't hate aphids, even though they are revolting.   Learn how they work.   When you get blackfly/aphids, you often see ants running up and down the plant, whether it is broadbeans or roses or whatever.   You know that ants FARM aphids?   They move the aphid eggs to the most vigourous, sugar-producing tip of the plant.   This is because aphids suck too much sap and get more sugar than they need, so they excrete the sugar.

In the South-East of England, by June, because it is hotter and drier, blackfly aphids are infesting the tips of the broadbeans.   You can pinch out the tips now, as popularly suggested, or you can use your fingers to rub out the blackfly.  If you hate touching them and squashing them, use a toothbrush.   These methods are more effective than spraying them with soapy water, I've found.  I wouldn't even dream of using a chemical spray, it isn't necessary, and it will unfortunately also kill the beneficial insects, the ladybirds and hoverflies and what not.

After about two weeks, the ladybirds and other aphid-eating insects catch up with the blackfly, and you don't have to worry about doing this job.  Every year, this two week period is all you have to worry about when it comes to blackfly on your broadbeans, if you let nature catch up with the blackfly.   When you start seeing ladybirds on your broadbeans, pat yourself on the back and congratulate yourself for doing a wonderful job.

[BabyStar]

I tried diluted washing up liquid before on something, I can't remember what, and it didn't like it at all, so probably not diluted enough!
The broad beans are probably about three feet high now and always loathe to pinch the tops of things as want them to get bigger and bigger! But guess it has to be done sometime...
They are collecting up in the top of the folds of new leaves. I see the ants farming them too! I am not keen on touching them, remember getting handfuls of them running a closed hand up the runner bean vines last year. They're like caviar!
Not seen too many ladybirds about this year but if they find my broad beans they will have a field day! Hopefully they'll be out and about soon.
Will persist with the spraying and pinch out the tips and touch wood will have get a good crop!