Our Hydrangeas have a white cased egg type bug on the back of the leaves and stems. What should I use to clear this up?

Hi Paul, this is Cottony hydrangea scale, a type of sap sucking insect that can be controlled by using a horticultural spraying oil which smothers the insect that is hard to make contact with as it has the fluffy covering to protect the insect. The oil can also be mixed with a compatible insecticide, talk to your local garden centre about a suitable control. Repeat sprays will be necessary to capture all stages of the insects lifecycle. If the infestation is really bad, you can cut out some of the worst affected parts of the plant. Lianne.