The horse chestnut scale insect was first found in the UK in the late 1960s, having come over from southern Europe. It is now widespread and common in the south of the UK and Ireland, and is spreading northwards. Mature, adult horse chestnut scale insects are up to 5mm long and can be found on the main trunk and branches. They drop off in summer, leaving white clusters of eggs.
Little damage is done to the host plant, but the insects can look unsightly. They suck sap from plants and produce honeydew, which can encourage sooty mould to develop. It’s more of a problem in urban areas where temperatures are higher.
Find it on
horse chestnuts, magnolias, cornus, bay, lime and acer trees.
Scrape the eggs off by hand and move them to an alternative tree, or destroy them.
Spray with an insecticide containing deltamethrin in midsummer.