London Borough of Merton arboriculture manager and London Tree Officers Association (LTOA) committee member Dave Lofthouse said: "Treatments carried out in the buffer zone by the Forestry Commission (FC) are efficacious where they are applied, but this is only on trees known to be infested in 2015. The large increase in areas infested cannot be dealt with at the level of funding applied to smaller areas in past years. It would be unrealistic to think we can eliminate or prevent the steady spread of the pest with such limited resources, when we have not in the past."
Stressing that this was "not necessarily an LTOA view", he said the FC-defined core zone "contains many parties who conscientiously treat infestations but unfortunately many who may not", adding: "This zone is therefore an inexhaustible reservoir of re-infestations making any current successes at best transitory."
The FC has been implementing its Defra-funded OPM control programme since 2013, initially for three years but extended for a further year for 2016. This identifies a core zone in west and southwest London where eradication "is currently impossible" and a wider control or buffer zone, covering most of the rest of Greater London as well as Reading, West Berkshire and South Oxfordshire.
But FC maps show that this year the core zone has been enlarged significantly, and now includes the central boroughs of Kensington & Chelsea and most of Westminster as well affected areas to the south, west and north. Statutory Plant Health Notices (SPHNs) are only routinely issued to owners of infested trees outside the core zone.
A DEFRA spokesperson said: "We are committed to protecting non infected areas and have invested over £21 million into tree health research. We estimate through our control programme in South London we have prevented spread to an area covering the homes of 3.5 million people."