Should I be worried about these insects?

This is my first spring as a gardener and my silver artemisia has been attracting these small insects on its new flowering branches. Does anyone know what they are and whether I should be encouraging them or getting rid of them? They don't seem to be affecting the plant as near where they are, the plant seems very healthy. Further away some of the leaves have gone a bit yellow and straggly, but that could be something else entirely causing that.

 

Here's another photo in case it's clearer.

 

Looks like blackfly to me, aphids.
You need to get rid of them.

How you do that depends on you, personally I'd give them a quick spray with an insecticide.

 

Thanks Pete. I'll take a look at what the options are. I thought artemisia was supposed to deter aphids though? They seem to be loving my one! I would post a link to where I read that, but I can't because I only just joined.

 

Cut your artemisia back now DominiH...or soon. This will rid your plant of aphids at the same time as regenerating it.
Use the cut pieces as cuttings......summer is ideal for this but you can still try it now. Use a mixture of multi purpose compost and perlite, 50/50, and insert 3” or 4” cuttings around the rim of a 9cm pot. Water and cover with a polythene bag

 

I find that silver-leaved cuttings rot off if covered with polythene

 

Do mine every year....no, they haven’t rotted off yet. The secret is to water cuttings in then keep them dry.

 

I'll continue to (successfully) root them without covering them, thanks anyway.

 

Thanks Verdun. Definitely seems like I can kill two birds with one stone that way.

 

Good morning DominiH....yes indeedy