Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae)

IEFC - Forest pests and diseases - Consult - <i>Dryocosmus kuriphilus</i> Yasumatsu (Hymenoptera, Cynipidae)

Chestnut gall wasp

Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae)

Host tree

Chestnut species (Castanea spp)


  • The numerous galls are easily observable on chestnut leaves and petioles. They are green-red in spring and summer and often remain as brown galls in winter.
  • Attacked shoots and leaves show reduced growth.
  • Heavily infested trees show a decline in crown density.
  • Adult wasps are very small and eggs in buds are hardly visible.


  • Heavy attacks lead to severe yield reduction both in chestnut orchards and in forests.
  • Severely attacked trees show signs of decline. It is not clear whether repeated defoliation may kill trees directly but attacked trees are more prone to chestnut blight.
  • Since D. kuriphilus is newly invasive in Europe, a proper assessment of its long term impact on the economy, society and environment is needed.


  • There is one generation per year.
  • Eggs overwinter in buds.
  • Galls containing several larvae develop in spring on young shoots and leaves, reducing their growth.
  • Adults fly from mid-May to July depending on the climate and lay eggs in new buds.

Risk factors

  • All chestnut trees in Europe are at high risk, although some cultivars appear more resistant.


  • Dryocosmus kuriphilus originates from China and was first found in Italy in 2002, from where it spread to other European countries: France, Switzerland, Slovenia, Hungary, Croatia, Czech Republic, Austria, the Netherlands, Germany, etc. Also invasive in the USA.

Pest management


  • Dryocosmus kuriphilus is a quarantine organism in Europe. The movement of chestnut plants in and from infested regions is regulated.

Preventive measurements

  • New infestations are usually only seen when galls are formed on the leaves, i.e. too late for eradication.

Curative control

  • Chemical control is difficult because larvae feed internally.
  • A biological control programme is presently being carried out in Italy and in France though the importation of Torymus sinensis, a specific parasitoid originating from China.
  • Not all chestnut varieties are similarly susceptible to the wasp. The development of resistant varieties is presently being considered.

Climate change

  • It is too early to assess the effect of climate change on this insect because it has not yet reached its potential distribution in Europe and its trophic relationships are still evolving.

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