Toxic caterpillar outbreak across southern England sparks health warning

Toxic caterpillars are spreading across London and south-east England, environmental experts have warned.

The larvae of oak processionary moths (OPM) are covered in long hairs which can cause skin and eye irritations, rashes, sore throats and breathing difficulties, according to the Forestry Commission (FC).

People have been warned not to touch the caterpillars, which can often be found in late spring and early summer in and around oak trees.

OPM can be spotted moving around in distinctive “nose-to-tail processions” according to the FC, as well as in “arrow-head” shaped groups.

The caterpillars have thousands of very long, white hairs which contrast with shorter hairs – these contain a protein called thaumetopoein which causes the health problems.

The FC has also urged people not to touch OPM nests, which are made of white, silken webbing and can often be spotted on the trunks and branches of oak trees – but almost never among the leaves.

There is an on-going government-led initiative to minimise the populations of OPM in affected areas, as the larvae damage trees when large numbers feed on the leaves, leaving them vulnerable.

A spokesperson for the Department for Environmental Food & Rural Affairs (Defra) told The Independent: “The Forestry Commission have a programme of work, a control programme to prevent the spread. It involves guidance, surveillance, treatment and research.”

The FC said this month it had identified more than 600 sites for treatment, each of which could include one or more trees.

“OPM caterpillars were spotted emerging from egg plaques in mid-April, so we began treating trees in the Protected Zone with an approved biopesticide during the week beginning Monday 23 April 2018,” it said in a statement.

“The treatment programme is expected to continue until late May or early June.

“After that the caterpillars will be too large to be affected by our preferred treatment product.”

First discovered in west London in 2005, it is believed that the outbreaks are likely to have begun after some young oak trees imported from Europe which already had OPM eggs on them.

OPM are native to southern Europe where predators and the environment kept their population in check.

Offering advice on what to do to stay safe, the Defra spokesperson added: “Don’t pick up a caterpillar or move a nest.

“Don’t let children or animals touch or approach nests or caterpillars or try removing them yourself.

“If you spot one you can get in touch with the Forestry Commission they can come and remove it.”

FC advice says people should consult a doctor or vet if a person or animal has had an allergic reaction or has been seriously affected by contact with the larvae.

Pharmacists can offer relief for skin or eye irritations.

A map of affected areas along with further information and advice is available on the Forestry Commission website.