Do Castanea sativa wild provenances influence Dryocosmus kuriphilus Yasumatsu 1 (Hymenoptera: Cynipidae) infestations?

The Asian Chestnut Gall Wasp (ACGW), Dryocosmus kuriphilus, native to China was accidentally introduced into many countries worldwide, including Italy. Different susceptibilities have been reported in literature among cultivated plants belonging to different gene pools worldwide, but this aspect has not been sufficiently explored among wild chestnut populations. The aims of this multi-year study were i) to assess differences in susceptibility to ACGW in wild C. sativa plants coming from different parts of Europe grown in an experimental plot in Central Italy, ii) to preliminarily analyse the relationships between temperature, relative humidity and rain variables of winter and summer and D. kuriphilus infestation. Provenances coming from Greece reported a significantly smaller number of galls than the Italian and Spanish ones in the three-years of survey, showing a lower susceptibility to ACGW attacks in respect of plants coming from Italy and Spain. Inter-annual variation of ACGW infestation in the chestnut provenances may be influenced by the local environmental conditions. A hot and dry summer, occurred in 2015, could be responsible for a marked decrease in ACGW population density during 2016. The results lead to suppose that the different genotypes considered have different reactions depending on environmental conditions and ACGW attacks.