Oriental Chestnut Gall Wasp

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

An overview of the 2015 discoveries of Dryocosmus kuriphilus (Oriental chestnut gall wasp; OCGW) in European sweet chestnut (Castanea sativa) trees in Farningham Woods, Kent and St Albans, Hertfordshire, was published in Quarterly Journal of Forestry. It was written by Dr Simon Morath and co-authors from Forest Research and Forestry Commission England.

It describes 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 were at the time 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 the species is widely planted and grown as a woodland species in South-East England. It is also valued as a street and parkland tree.

Much sweet chestnut is also coppiced for timber, especially in Kent. Analysis of OCGW galls by Forest Research has shown that OCGW infestation is likely to have little effect on timber quality. However, galls might increase the likelihood of infection from sweet chestnut blight, caused by the fungus Cryphonectria parasitica.

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 Hertfordshire 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. It 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

PDF copy of article provided by kind permission of The Royal Forestry Society ©

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