Dangerous caterpillars breeding in Brentwood

Mick Ferris

A type of caterpillar that can cause breathing difficulties if come into contact with has been found in Brentwood.

Brentwood Borough Council is warning people that oak processionary moths  – a species of moth with caterpillars that nest on oak trees – have been found in areas including Hutton Recreation Ground, Navestock, Thorndon Park and the A128 near Halfway House.

The Forestry Commission is to start work treating a number of trees in the next few weeks where the insects have been located.

The caterpillars are covered in small hairs which can cause health risks in humans.

The caterpillars hatch in spring and go through several instars – eventually developing the irritating hairs.

The caterpillars descend lower down the tree as they develop, stripping the tree of its leaves as they go, leaving it vulnerable and weakened.

In the summer, they retreat into nests and pupate. The adult moths emerge in late summer, living for only four days in order to mate. The female lays her fertilised eggs high in the tree canopy and the cycle begins again.

Older caterpillars develop tiny hairs containing an irritating protein called thaumetopoein. Contact with the hairs can cause itching skin rashes and eye irritations, as well as sore throats and breathing difficulties in people and animals. The risk of exposure to these hairs is highest in May and June.

The caterpillars can shed the hairs when threatened or disturbed. The hairs can be blown by the wind and they accumulate in the caterpillars’ nests, which can fall to the ground. They can stick to trunks, branches, grass and clothing as well as to equipment, such as ropes, used by tree surgeons and forestry and ground-care workers.

Mick Ferris

Editor Email: mickferris@yellowad.co.uk