Oak processionary moth caterpillars are threatening English oak woodlands. A recent outbreak in a Croydon woodland confirms that the pest has spread from its first sighting in Richmond, near Kew Gardens, in 2006.
The oak moth caterpillars (Thaumetopoea processionea), which swarm in large numbers, eat both the leaves and bark off the trees and create large webbing nests in tree canopies. It is called a processionary moth as the caterpillars move from tree to tree across the ground in a long, nose-to-tail ‘conga line’.
Apparently some of the Croydon caterpillar nests were so large that a spell of wet weather caused them to drop off the trees, spreading caterpillars all over the ground. This is bad news for anyone underneath as the stinging hairs on the caterpillars can cause severe skin irritations, affecting some people so badly they need hospitalisation. The Forestry Commission’s Andrew Hoppit said “The numbers were so intense – it was like something out of a science fiction movie.”
The oak processionary moth originates in the Mediterranean and has no known predators in the UK. Infestations can severely debilitate trees and make them more susceptible to other diseases. An area of about 2km around Croydon has been sprayed with a bacteriological agent that destroys both the caterpillars and their nests. Pheromone traps set by the Forestry Commission confirm that the oak moth is spreading but that the spraying is having an effect on total numbers.
It’s believed that eggs of the oak processionary moth arrived in England on oak imported by Kew Gardens in 2006. The moth caterpillar has also been seen in Berkshire. Anyone finding a suspected oak processionary moth caterpillar nest should not try to deal with the pest but contact the UK Forestry Commission.