Oriental Chestnut Gall Wasp

News of a recent unwelcome discovery and how ‘citizen science’ can play an important role in surveying and identification

Oriental sweet chestnut gall wasp (Dryocosmus kuriphilus, gall wasp, chestnut gall, chestnut gall wasp, oriental chestnut gall wasp)In an overview of the recent discoveries of Dryocosmus kuriphilus,  Oriental Chestnut Gall Wasp (OCGW) in Farnigham Woods, Kent and St Albans, Hertfordshire, published in Quarterly Journal of Forestry,  Dr Simon Morath and co-authors from Forest Research and from Forestry Commission England describe the life cycle and symptoms of OCGW and its invasion history from its probable country of origin – China – to Japan, Korea, eastern USA and Europe. Although widespread in Europe, these two outbreaks are thought to be the only recorded cases of OCGW in the UK.

The tree health implications of OCGW in the UK are discussed. The UK is not a major producer of sweet chestnuts but sweet chestnut is widely planted and grown as woodland in the south east of England. It is also valued as a street and parkland tree. Much sweet chestnut is coppiced. Analysis of OCGW galls by Forest Research has shown that OCGW infestation is likely to have little effect on timber quality. OCGW galls might increase the likelihood of infection from sweet chestnut blight (Cryphonectria parasitica), but this is a quarantine organism and is now considered eradicated in the UK.

The surveys undertaken and the response to the outbreaks are described and future management of the pest is considered. Of particular note is that the Hertforshire outbreak was identified by an Observatree volunteer. Observatree is a collaborative citizen science project, led by Forest Research, involving several partners and funded by the EU’s Life+ Programme that trains volunteers to provide a tree health early warning system.

Morath, S., Fielding, N., Tilbury, C., Jones, B. (2015) Oriental Chestnut Gall Wasp. News of a recent unwelcome discovery and how ‘citizen science’ can play an important role in surveying and identification. Quarterly Journal of Forestry 109 (4), 253-258

Print copy only; pdf copy of article provided by kind permission of The Royal Forestry Society ©