Wisteria Scale, Wisteria Soft Scale
Wisteria Scale is a species of soft-bodied scale insect. Scale insects are true bugs, and they feed by sucking the sap from plants. Eulecanium excrescens targets Wisteria but can be found on Acer and Prunus, too. They are relatively large for a scale insect with each female reaching up to 1cm. They produce a cottony white wax, which protects against parasites and desiccation but also protects against pesticides.
Heavy infestations may impact plant vigour.
Adults: Matured adults are most active in late spring. The adults are quite unsightly, appearing circular, convex and dark grey in colour. A white, cottony wax dusted over them and the infested area may be evident. It's much larger than any other British species. Nymphs: Immature scale insects are pinky brown and smaller in size, less convex in shape. Tip: A simple trick in distinguishing Wisteria scale from others: brown scale is a chestnut brown and ovally shaped, whereas nut scale much smaller in size.
Infested plants can lose vigour as a result of the suck-sapping activity. A black sooty mould can begin to form on the plants' surfaces as a result of scale honeydew secretions. Moulds can attract further infections from other sources in the environment. Excretions of honeydew can cover the surfaces of infested plants.
The UK, USA; native to Asia
Well-tended Wisteria is often healthy enough to withstand light infestations. Any scale that's seen may be scraped off and disposed of accordingly. The presence of natural garden predators, like parasitic wasps and ladybirds, means that treatments aren't necessary most of the time. Attract beneficial insects into your garden by providing 'wild patches', hanging baskets and log piles.
For heavier infestations, there are a large variety of organic sprays and winter wash products available for use in UK garden centres. There are more persistent chemicals available on the market for use if infestations are more substantial. Vines can be challenging to treat sometimes, especially if they stretch vast distances. Assess the damage concerning the size of the plant. Older, more established plants can withstand infestations. If you do choose the above products: spray treatments are best applied early in the year when nymphs are still newly hatched and more susceptible to the chemicals. Always attempt to scrape away any dead scale before applying any treatments. Plants that are in flower should never be sprayed to avoid harming beneficial insects.