Hydrangea scale is a “sap sucking” insect, according to the Royal Horticultural Society (RHS). It is found on hydrangeas but can also feed on other woody plants including acer and prunus. The RHS said ...

Neglected hydrangeas that have never been properly pruned eventually become a nightmare of congested branches, often flecked with white blobs of hydrangea scale and masses of small, withered flower ...