Insects and diseases affecting trees and hedges

Trees and hedges may be affected by a range of diseases and insects.

To read more about these, visit the Forestry Commission website.

Ash dieback (Chalara fraxinea)

Ash dieback is a serious disease caused by a fungus called Chalara fraxinea. The disease causes leaf loss and crown dieback in Ash trees, and usually leads to tree death.

Young trees cannot recover from infection, but mature trees can survive for a considerable time and some may recover entirely. The impact of Chalara fraxinea depends on tree age, location, weather conditions and co-presence of honey fungus or other pathogenic organisms. Though currently there have been no confirmed cases within the M25 London circular.

Oak Processionary Moth

The Oak Processionary Moth (Thaumetopoea processionea) is an invasive species which has health implications to trees, humans and animals. Native to central and southern Europe, this pest has been identified in London and is breeding on oak trees in West and South London. It gets its common name from its caterpillars' striking habit of forming long lines, or 'processions', in trees and other substrates. The area affected by Oak Processionary Moth is growing steadily and has been identified within Kingston Upon Thames and neighbouring boroughs.

You must not attempt to handle the larvae caterpillars yourself, or disturb their nests.

The caterpillars have irritating hairs that carry a toxin which can be blown in the wind and cause serious irritation to the skin, eyes and bronchial tubes of humans and animals. They are considered a significant health problem.