Why do you want to cut it down so low? It’s very unlikely to kill it but you'll lose a lot of flowers. (Assuming we’re talking about a hardy magellanica).

floral

My rationale is simple.

At least 50% of the plant is affected by the mite.

Removing the damaged shoots will not guarantee that other shoots which appear clean have not already been infected.

Quite a few of the shoots that are bearing flowers are showing signs of being affected

Remove all of the plant to 6", or at least to clean wood, will remove ALL foliage and hopefully, all of the mites. This could be followed up with a "wash down" of the plant with White Oil or similar.

I lose the flowers this season, but there is always next year.

It isn't a plant I would write home about, but it is filling a hole.

If the mites return after surgery, out it will go. Bye bye

Fof

Right. What a mess. Chop away.

Ended up cutting to just above ground level, as every breaking bud was infested. The whole area surrounding it, was swept clean of every trace of loose vegetation, leaves, twigs, etc.

The stumps were then smothered in a mixture of veg oil and washing up liquid, with a small dash of water.

Sink or swim, baby. :-))))))