Horse chestnut scale insect

Symptoms

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.

Time to act: May-September

Problem categories

Overview

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.

Solution

Organic

Scrape the eggs off by hand and move them to an alternative tree, or destroy them.

Chemical

Spray with an insecticide containing imidaclprid or thiacloprid in midsummer. Both imidacloprid and thiacloprid are systemic pesticides, meaning they are absorbed into the plant and can be present in concentrated forms in the nectar and pollen of flowers. If you do use these chemicals, bear in mind that any bees that visit the flowers may be killed by traces of these chemicals in the pollen and nectar.

Discuss this problem

Talkback: Horse chestnut scale insect

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gail255963 24/11/2011 at 15:29

i have just found the answer to a problem i have had for a good few years on my acer trees!!!

gardeners world has answered my question the bugs are the HORSE CHESTNUT SCALE INSECT!!!

Each year i just hose them off, is this an ok solution? i don't really like to use chemicals.

Thankyou for the information
kind regards
gail b