Clusters of insects covered with the protection of a waxy shield, which attach themselves to the older stems of the plant. If infestation is bad the whole cane can be covered so thickly no bark can be seen between the insects. Scale mostly affects older wood of the rose which would normally be cut away with yearly pruning. If scale is heavy the old wood has probably not being pruned.
To control you can spray heavily with soapy water, ‘Pest-Oil’, or ‘Eco-Pest Oil’ to smother the insects with the oil or soap. May need to do several times. Ants move the scale around the plant, so eliminate the ants that ‘milk’ the scale.
Can use ‘Confidor’ but soap or oils usually work. Not one of the most damaging rose insects but control should be undertaken to avoid more severe problems in the future.