What do you think about – Pyrethrum? (And a bit about black aphids)

I have an ongoing problem with black aphids in my garden.  They lay waste to my spring onions, garlic chives, normal chives, garlic (when I grow it) and pretty much anything else I plant in the allium family.

Black aphids thrive in moist conditions and particularly enjoy weaker plants.  Because my garden gets less than full sun I think my plants are particular susceptible.

Here are some attacking a baby garlic chive plant:

I have tried squishing them.  I have tried spraying them off with the hose (a technique I find effective with normal aphids).  I have tried chilli and garlic sprays.  No success.  The only thing I can find that gets rid of them is pyrethrum.

Hence the question – should I use it?  I know it’s generally considered a ‘safe’ pesticide, but not necessarily by everyone.  I also know it can kill beneficial insects if they come into contact with it.

So should I use it?  Do you use an insecticide?  Or another method for containing the bugs?