Trees, Shrubs and Conifers: Scale insect on Physocarpus, 0 by HoosierGreen

HoosierGreen wrote:
I don't know if it's available in France, but Bayer makes an excellent systemic insecticide that is derived from tobacco (nicotine), so it's pretty much "organic". It's called Bayer 12-month Tree and Shrub Insect Control and Fertilizer. It's works wonderfully well and you have to apply it (mix and pour around the base) only once per year. In this country, it's readily available and very inexpensive. (see photo)

Alternatively, you can apply a summer-weight horticultural-grade oil to the plant. It's completely organic and should smother the scale, especially the babies at the crawler stage.

Note: Are you sure it's a scale infestation? Ninebarks are notoriously pest-free.