Asian wasps swarm threatens trees

by | Jun 22, 2015 | Featured Slider, Latest, News

Chestnut trees are under threat after an outbreak of Asian wasps was spotted for the first time in the UK.

The Forestry Commission issued an alert yesterday after a sighting of the oriental chestnut gall wasp (OCGW) was confirmed at Farningham Woods, Kent.

Sweet chestnut trees, or Castanea, are under threat from the tiny wasp, whose larvae cause growths called galls to form on the leaves, leaving the tree susceptible to disease.

The pest, which is up to 3mm long and has a black body, translucent wings and orange legs, is parthenogenetic, meaning males are not needed to reproduce.

The wasps have no sting and pose no risk to humans, pets or livestock.

The galls can be controlled with insecticide but this is unlikely to help in outbreaks. Another option is to fell and burn affected trees.

The tiny wasp, native in parts of Asia, has been accidentally introduced across Europe but it is unknown how it entered Britain.

Severe attacks could result in the loss of trees while damage to sweet chestnuts could have a negative consequence on woodland biodiversity.

Despite only one known sighting at Farningham, Britain’s suitable climate and the popularity of sweet chestnut trees has heightened fears of an epidemic.

Surveillance against the wasps have been carried out in nurseries and orchards since 2006 but yesterday’s outbreak remains the only one ever detected.

A five-kilometere area of affected woodland is being surveyed while investigations are also taking place to see how the pest could have entered Britain.

At risk: The wasps’ larvae cause growths called galls to form on the leaves, leaving the tree susceptible to disease

Susceptible: The Forestry Commission has launched an investigation of the Kent woods, as the wasp could cause a negative impact on woodland biodiveristy

A Forestry Commission spokeswoman said: ‘It does not sting or bite, and does not pose any risk to people, pets or farm livestock.

‘We have launched an immediate investigation of the surrounding woodland and, once we have fully assessed the situation, we will swiftly take any appropriate action.’

The Forestry Commission is also checking all shippings of the sweet chestnut tree into the UK to check for the bug.