Cryphonectria parasitica detected in abandoned galls of Dryocosmus kuriphilus
In the literature, it has been suggested that exit holes produced by Dryocosmus kuriphilus (Hymenoptera: Cynipidae – EPPO A2 List) could be entry points for Cryphonectria parasitica (EPPO A2 List), the causal agent of chestnut blight. In the United Kingdom, during surveys for C. parasitica conducted in 2018-2019, both pests were detected on 26 sites in London and West Sussex. Sweet chestnut (Castanea sativa) twigs bearing abandoned galls of D. kuriphilus were collected to verify the possible presence of C. parasitica (isolation, molecular testing). Out of 17 collected twigs, 10 tested positive for C. parasitica and all had been collected from London. In 3 cases, it was possible to isolate C. parasitica from the galls in pure culture. In one of the samples, the twig with D. kuriphilus galls also showed a typical canker of C. parasitica. These results show that abandoned galls of D. kuriphilus can be colonized by C. parasitica. However, it is noted that further studies are needed to determine the interaction between D. kuriphilus and C. parasitica, and how this relates to the disease incidence.
Sources
Pérez-Sierra A, van der Linde S, Romón-Ochoa P, Jones B, Gorton C (2020) First report of Cryphonectria parasitica on abandoned galls of Dryocosmus kuriphilus on sweet chestnut in the United Kingdom. New Disease Reports 41, 34. http://dx.doi.org/10.5197/j.2044-0588.2020.041.034