Hydrangea scale is a

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.

The immature scales (nymphs known as crawlers) are difficult to see and the presence of these insects becomes apparent in early summer when the adult scales deposit eggs on the stems and leaves. You may see:

• Eggs which are covered in white waxy fibres that form smooth, oval patches 3-4 mm long. These white patches will persist on the plant long after the eggs have hatched
• Newly hatched scales (crawlers) are less than 1 mm long and are pale yellow
• The crawler stage can be distributed in wind currents
• The mature scales are around 3 mm in diameter, oval in shape and brown
• Heavily affected plants lack vigour and may shed leaves 

• Where possible tolerate populations of scale insects. Well-tended healthy plants are able to tolerate light populations of these insects and so they do not necessarily require management
• Encourage predators in the garden, some ladybirds, parasitoid wasps and some birds will eat scale insects
• Adult scales and egg masses can be removed when seen but this may not reduce large populations
• Heavily affected plants can be removed and replacements planted in the autumn

Hydrangea scale is a sap-sucking insect that develops on the underside of leaves on Hydrangea and some other plants.

There is one generation a year with young nymphs hatching from eggs in mid-summer and sucking

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.