Toxic caterpillars that cause rashes are spreading across England – how to spot them
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Britons are being urged to watch out for a ‘dangerous’ species of venomous caterpillar that can cause itchy rashes and asthma attacks.
The ‘oak processionary caterpillar’ is an invasive caterpillar that strips England’s native oaks of their leaves and poisons humans, horses and dogs.
Experts warn that the species is most active during the summer months, so the public should be on the lookout for their huge white silk communal nests.
Having arrived in London from Europe nearly 20 years ago, the species is spreading rapidly and could reach Birmingham in just over 10 years.
Last year, 255 Britons became ill from the caterpillar, compared to just 12 in 2014 and 55 in 2019, Staatsbosbeheer recently revealed.
Oak processionary caterpillars get their name from the fact that they form a curious nose-to-tail procession as they make their way from the ground to an oak tree (pictured along the ground)
Staatsbosbeheer is now urging the public to report sightings of the caterpillars or their nests through it online Tree Alert tool.
The nests — which are white and average the size of a tennis ball — contain hundreds of caterpillars, which have black heads and grow to about two inches long.
Each caterpillar is covered in thousands of hairs that can be carried in the wind, all of which contain a toxin called thamentopoin.
Contact with or inhalation of the hairs can cause painful skin rashes, eye problems such as conjunctivitis, vomiting, dizziness, fever, and respiratory problems such as pharyngitis and asthma.
“The risk of exposure to these hairs is highest in May and June,” Staatsbosbeheer says on its website.
“The groups most vulnerable to health risks include curious children, curious pets, people who work on or near oak trees, anyone who spends time near affected trees, and grazing livestock and wildlife.”
The oak processionary caterpillar – officially called Thaumetopoea processionea – is particularly common in Greater London and the South East of England, although they are spreading at an alarming rate.
Experts from the Forestry Commission believe the species will reach Bristol and Birmingham by 2035 and may eventually reach as far north as the Humber.
“We are moving from an urban situation to the wider area or the countryside – it makes it much more challenging,” said Andrew Hoppit, oak processionary caterpillar project manager at Staatsbosbeheer. the times.
Right now, the best way to control populations is to spray a biopesticide that contains a bacteria that kills the caterpillars when they ingest it.
Experts warn that the species is most active during the summer months, so the public should be on the lookout for their huge white silk communal nests.
Oak processionary caterpillars can cause severe skin rashes (pictured), asthma attacks, eye irritations (including conjunctivitis), throat irritations, vomiting, dizziness and fever
According to Hoppit, it’s the caterpillars and their hairs that pose the danger, not the moths, which only live for one or two days.
Still, it’s important to track the moths’ flight, as they lay the eggs that grow into the caterpillars – although this is difficult to do.
“It’s a little brown moth that flies at night and is very hard to find,” Hoppit said.
The expert recommends that adults look out for oak processionary caterpillar nests when they are near oaks, especially if they are with children or dogs.
“Please don’t go near the caterpillars – especially children who can get quite interested in the processions and especially the furry nature of them,” he said.
“They look cute, but unfortunately they can cause nasty rashes and conjunctivitis.”
Much of south-east England has been conquered by the caterpillars since they were first accidentally introduced to London in 2005 or 2006.
Since then, the pest has spread across the capital and into Kent, Essex, Berkshire, Bucks, Surrey and Sussex.
The species gets its name from the fact that the caterpillars form a curious nose-to-tail procession as they crawl across the ground and up an oak tree
Andrew Hoppit, oak processionary caterpillar project manager at Staatsbosbeheer, says the public should avoid hairy caterpillars as they “could be dangerous”
The adult stage of the oak processionary caterpillar (officially called Thaumetopoea processionea). It is important to monitor the moths to better understand where they lay their eggs
The species gets its name from the fact that the caterpillars form a curious nose-to-tail procession as they crawl across the ground and up an oak tree.
Despite feeding on the leaves of an oak tree, they never nest among the leaves and are instead found on the trunks.
Eating their leaves negatively affects the oaks’ growth and makes them more vulnerable to other stresses, such as drought.
After feasting on the trees, the caterpillars return to their nest in late July, where they form a cocoon before turning into a moth.
Hoppit said the public should stay away from hairy caterpillars because they “have the potential to be dangerous.”
WHAT ARE OAK PROCESSIONARY MOTHS?
The oak processionary caterpillar (OPM) is a non-native moth that has become established in parts of London and surrounding areas.
It can defoliate oak trees, but its main concern comes from their 63,000 hairs.
They are distinguishable by their incredibly hairy bodies and white, silky nests on oak trees.
Hairs on the caterpillars, which feed on oak trees, contain toxins that cause severe dizziness, fever, and eye and throat irritation.
The oak processionary caterpillar lays its eggs on oak trees and its larvae leave their nests to feed on oak leaves.
Once they cut down a tree, they move on to the next tree – following each other in a procession, hence their name.
The pests settle on oak trees, leaving white, silky trails about the size of a tennis ball