"The line is definitely not holding" in measures to control the spread of oak processionary moth (Thaumetopoea processionea, OPM) in south-east England, according to a contractor that specialises in controlling the hazardous invasive tree pest.
Mark Townsend, general manager at Gristwood & Toms, told HW: "The view from people in OPM control has been for some years that eradication is not possible. They are flying insects and it only takes one or two pioneers to create a golf ball-size nest in an oak tree (for the problem to spread)."
Gristwood & Toms has dealt with the problem for several London boroughs as well as for The Royal Parks, based on control techniques that have been developed in the Netherlands.
"Every county in the Netherlands now has OPM," said Townsend. "As here, the population waxes and wanes with the conditions. They tend to treat it on a risk basis rather than with blanket control measures.
"It's a bit glib to put it down to climate change. It got here on trees in the back of a lorry. Our climate is similar to Europe's, where it has spread up and down, as far north as Sweden. It can survive harsh winters. All it needs is temperate weather and oak trees, and we have both in abundance. I can't see why it won't cover the country."
The Forestry Commission has for two years pursued a strategy of containing the problem within a control zone in south-west London and attempting to eradicating it elsewhere.
A commission representative said the strategy remains in place. "We are in the last year of a three-year Defra-funded pilot project for OPM control and no decision has yet been taken on the control strategy and resourcing for future years."
Health effects - More outbreaks anticipated
In June, Public Health England published a report on the health effects of oak processionary moth. The paper advised better guidance for treatment as well as increased awareness among GPs, pharmacists and "occupationally exposed individuals" in affected areas "in anticipation of further outbreaks".
"Arboriculturists and other individuals who work in and among oak trees ... have a greater risk of becoming sensitised due to their repeated exposure to OPM setae (hairs)," the report stated, adding that individuals do not appear to show particular susceptibility, as with other allergic reactions.
However, it noted: "The evidence from continental Europe (on the public health impact) is generally reassuring."