What is this on the stems of my rose?

I have many roses in my garden and the majority are from David Austen.

I am on the South Downs so garden on chalk. All the roses have flowered magnificently for years now.

So I prepare the ground really well, and never plant in soil that has previously supported a rose. Lots of water in first year - all mostly in sun, although there are exceptions.

I feed early spring and mid summer. And quick size reduce prune in early autumn (wind) and proper prune late Feb - Mch.

That’s it

I have two potted roses and neither of them have done spectacularly well this year. I am just now seeing signs of a second flush on one of them - a David Austin rose - but the other one is struggling and I can’t see it doing anything else this season. In its first flowering, the flowers were very poor compared with previous years.

Hope the ericaeceous food helps, Witzend. I am amazed at the difference it's made to my potted rose.

Thanks, all. I googled scale insects and have ordered Neem spray, which is supposed to get rid of them.

I will try the ericaceous feed, too, Aldom!

I would agree with scale insects. An infestation often affects roses under stress due to environmental conditions, inadequate watering or poor drainage.

Could that be a bad attack of rose scale insects?

I recently read that roses like acid soil.
One of my roses which is in a pot has been in poor condition for a couple of years. I was even thinking of disposing of it.
I decided to feed the rose with ericaeceous feed as well as rose food. The transformation is incredible. No disease, shiny, healthy folliage and and abundance of flowers. All in a few months. I'm delighted.

Sympathy, Witzend… our repeat-flowering climber has not flowered a second time apart from 2 flowers…

The hot and dry weather is the culprit apparently. Sorry not to help with identifying the white particles…