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Oriental chestnut gall wasp

Oriental gall wasp was discovered for the first time in Britain in June 2015.

What is oriental chestnut gall wasp?

Oriental chestnut gall wasp is a species of gall wasp native to China which causes distinctive growth irregularities, or galls, to form on sweet chestnut trees (Castanea sativa) but does not affect horse chestnut trees. It was first discovered in the UK in Kent, in June 2015. A 2016 Forestry Commission survey found the oriental chestnut gall wasp in several locations in London and the South East.


  • Growths (galls) formed by the larvae of the oriental chestnut gall wasp on young leaves and twigs
  • Galls are between five and 20mm in diameter and green or rose pink, turning red or brown with age
  • Distortion and deformity of leaves


  • Oriental chestnut gall wasp laying eggs in the growth of sweet chestnut trees during the summer


  • Can cause a reduction in growth and fruiting
  • There may be some leaf retention around the galls
  • Galls that have developed on twigs can remain on the tree for two years or more

Oriental chestnut gall wasp does not bite, sting or pose any other threat to people or animals.

Report it

If you think you’ve spotted this disease please inform the Forestry Commission using the Tree Alert reporting tool. Three good-quality digital photographs are required to aid identification.

For more information visit the Forestry Commission.