Success of an exotic gallmaker, Dryocosmus kuriphilus, on chestnut in the USA: A historical account

Dryocosmus kuriphilus, a cynipid gall wasp of Asian origin, was accidentally introduced into North America in 1974. The gall wasp attacks chestnut and causes rounded galls that reduce shoot elongation and fruit production, and cause twig dieback. Its geographic range in the eastern USA has expanded northward since its introduction, and now encompasses nearly 1.5 million square kilometres. Movement of infested plant material has allowed the establishment of separate satellite populations well removed from contiguous populations. The cryptic nature of the insect, lying within dormant buds for much of the year, makes the effectiveness of plant inspections questionable. An introduced parasite, Torymus sinensis, has successfully moved with expanding D. kuriphilus populations, and several native parasitoids are exploiting this exotic gallmaker.