Help!!! What are these nasty bugs?

These are not particularly good photos (camera having trouble focusing) of what appear to be nasty bugs on our roses. We only spotted them after one stem has died. It looks as though the whole stem and leaves have been burnt.

They're about the size of a small ladybird and there are quite a lot on each stem






When we touch them they just fell fairly solid and when we push them with the edge of the secateurs they seem to be fairly firmly stuck and then just shoot off as though we have fired them from a gun. I think that's just from being forced until they pop off.

They appear to be hollow hemispheres but, at first, it seemed as though they were full of dust until you look closer. Then they seem like miniscule eggs.


All these white 'eggs' came from that husk.


Are they nasties?
Do I spray them with bug spray (we don't normally use any chemicals in the garden unless it's imperative)?
Do we cut them down to the ground and burn them?

The rose bed has dozens of these bushes, has been there between 50 and 70 years and the stems have thousands of very fine thorns.

We hope to solve the situation as soon as possible so thanks in advance.

 

Thanks @Palustris Does it matter which one and does a spray get rid of them?

 

Thanks everyone.

We'll try to knock them all off but it's a 20ft long bed of Rosa rugosa and they're very tightly packed with thousands of small thorns on every stem. Otherwise it means resorting to chemicals which we don't like to do. A friend has given us a bottle of Provado Ultimate Bug killer. I guess that would do it - if we can get the spray through the dense surface foliage. I presume that would work systematically anyway but I guess it would work quicker if we could get it through to the lower levels.




Rosa rugosa has a very strong scent which makes it perfect for being by our back door. Fresh multiple blooms on the top each day



In the past we've never worried about the small amount of bugs we get on them, as above, but these scale bugs are actually killing the plants.

I'll give it a go today - if I can find a sprayer.