April 03, 2012
Hydrangea Scale - Pulvinaria hydrangeae
The adult female scale is oval and about 3mm long. Towards the end of spring the females begin to produce ovisacs - structures of soft, white wax to hold the eggs. These usually end up about 10mm long but may be as long as 16mm. The dead female scale can be seen at one end of the ovisacs.
When the eggs hatch, the young scales or crawlers settle under leaves and on stems, sucking sap. When winter arrives they enter a resting stage and only become active again in the spring when they feed and finally reach the adult stage.
PLANTS ATTACKED - Hydrangeas, camellias and some other plants.
Infestations may be noticed only when the ovisacs are produced. Control is difficult at this stage because of the quantities of wax present. It would be better to wait until most of the eggs have hatched in the early summer and then spray with white oil at the rate of 25mL per litre per litre of water. If the plants are in flower use only 15mL per litre of water. It is necessary to thoroughly cover the undersides of the leaves and the stems.
About four weeks after spraying, inspect the plant to see how successful the operation has been. Dead scales will dry and produce a thick liquid if squashed. Living scales produce a watery liquid, and if many of these occur spraying should be undertaken again.