Multi-million-pound bill for tackling spate of diseases and pests affecting Herts’ trees

Photo courtesy of the Forestry Commission/Matteo Maspero (Image: Forestry Commission/Matteo Maspero)

Two years ago St Albans was pinpointed as the second place in the UK to suffer an attack by an exotic species of wasp which severely damages sweet chestnut trees.

The Forestry Commission served notice on Herts county council (HCC) after oriental chestnut gall wasps, a virulent pest, were found in 30-year-old trees lining Ashley Road.

A report for a recent environment planning panel meeting said that the removal and incineration of nine sweet chestnut trees, in line with ‘bio-secure’ measures, cost the authority £52,000.

With the county facing the threat of an “increasing number of tree pests and diseases”, officers warned councillors that the corporate risk was deemed as ‘severe’.

Gall wasp. Photo courtesy of the Forestry Commission/Matteo Maspero (Image: Forestry Commission/Matteo Maspero)

They admitted: “Prevention is not a realistic option or strategy. Until a better estimate has been reached regarding the number of trees the authority may have to deal with and over what timescale, costs are impossible to predict.

“The potential liability is anticipated to be over £10 million across a number of years.”

The Countryside Management Service has been allocated £50,000 to spend over the next two years to establish and manage a ‘tree health network’ across Herts.

Tree pests and diseases are affecting - or have the potential to affect - an increasing range of native trees gracing urban parks, streets and gardens, woodlands, lining highways, or growing in schools and nature reserves.

The environment panel was told that there are confirmed cases of fungal disease, Chalara ash dieback, “in the wider environment in all four corners of Herts”.

Ash dieback, an extremely aggressive fungus, is firmly established in St Albans district, and neighbouring areas. It has caused the widespread death of ash in Europe, where it is estimated that up to 90 per cent of trees in some areas have been affected.

Unfortunately, there is currently no treatment for the fungus, and with ash being this county’s most common tree, growing in urban and rural locations including parks, council officers said it had “potentially significant implications for the county’s landscape, biodiversity and rural economy”.

Despite the threat, the government has apparently indicated there will be no financial help available to deal with the problems caused by Chalara, and the impact on local authority resources.

HCC owns and is responsible for about 150,000 highway trees, the majority of which are in urban areas.

The authority’s highways contractor has a budget of £250,000 to survey the 15,000 ash trees lining roads.

By spring this year, following a review, the extent of the potential liability of the council’s ash tree population in relation to people and property will be known.

Meanwhile, oak processionary moth infestations were discovered in Watford and Hertsmere last year.

The health of oak trees becomes weakened after leaves are stripped, exposing them to the effects of other pathogens. The caterpillar is a pest because it is a hazard not only to the species, but to human and animal health as well. They have thousands of hairs containing a toxin which can cause highly irritating skin rashes, sore throats and, in some cases, breathing difficulty and eye problems. Their hairs are shed in a silken nest made by the caterpillar, making the pest and their nests a risk to public health.

And although the council removed the nine gall wasp-afflicted sweet chestnut trees from St Albans, “this response has not restricted the pest’s progress across much of south east England, including three new sites in Hertfordshire”.

The panel was told that such ‘threats’ were due in part to the increase in world trade in plants and plant materials, and exacerbated by climate change.