Hydrangea Scale is a type of soft scale that targets the stems and foliage of Hydrangea. It has also been recorded on Acer and Prunus genera. Soft scale insects make up a large and diverse family. They behave similarly to insects like aphids, or suckers, which eat by sucking sap from plants through a needle-like tube. Like aphids, they secrete a substance known as 'honeydew'; this can be problematic because it encourages the growth of sooty moulds.
Heavy infestations may reduce vigour.
Adults: The females are brown, oval and sessile, so are permanently attached to the tree. Nymphs: Newly hatched scales, or the first instar of scales, are only 1mm big and yellow. They are termed crawlers because they are able to move around the plant to find the best place to begin feeding. Eggs: Under the film shell, under a white and fluffy substance.
Plants may appear less vigorous. Honeydew on leaves. Black sooty moulds on leaves. Premature leaf fall. Wilting, sad-looking plants.
Asia, Europe and North America
By encouraging wildlife to visit your garden, you can attract natural forms of biocontrol to keep pests at bay, which are free of cost! Scraping off the scale may be attempted, but will be ineffective for heavy infestations.
As they have a hard waxy covering they are difficult to kill with pesticides. It has been suggested to apply chemical treatment in July when nymphal stages are present and more vulnerable to sprays. If you do decide to go down the chemical route, make sure to consult with your local garden centre, research well and read bottles carefully. Pesticides should never be applied to flowering plants because they can do harm to beneficial insects. Please consider if chemical control is really necessary. If a chemical option is sought, check with your local garden centre and please take care to follow the manufacturers' instructions. Check with your local regulating body for guidance on active ingredients and their authorisation for use.