The Asian Chestnut Gall Wasp in Italy: Surveys on its Native and Exotic Parasitoids as Well as on Chestnut Cultivar Susceptibility

Abstract

In the context of biological control against the Asian chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) in Italy, the aim of this study was to survey its native parasitoids as well as the exotic Torymus sinensis Kamijo which had been introduced and released as a biological control agent. Furthermore, both parasitism and pest susceptibility of local chestnut trees were investigated. Surveys were carried out in 2014 in the Municipality of Sambuca Pistoiese (Pistoia), in a chestnut forest which included three cultivars: Nerattino, Carpinese, and Pastinese. On a total of 35 trees, selected among the three cultivars, 24 current-year shoots were randomly collected and examined in the laboratory. After the damage by the cynipid had been assessed, leaf samples were used for molecular analyses. Galls were also collected on the 35 selected trees both for dissection and to rear parasitoid specimens in the laboratory. The three cultivars were confirmed by genetic tests. The Carpinese cultivar resulted to be the most damaged, with highest percentage of attacked shoots (84.38%). Moreover it was also the cultivar with the lower parasitism rate (about 16%). From reared galls seven parasitoid species emerged, all belonging to the superfamily of Chalcidoidea. Exception made for the non-native T. sinensis, the other six were native species associated to oak gall wasps. Native parasitoids were more scarcely present, while the exotic T. sinensis amounted for the 84.27% of all emerged parasitoids. Our results confirm how chestnut susceptibility to D. kuriphilus varies depending on the cultivar. Overall, the Nerattino cultivar resulted as the best among the three examined: it was subject to a less intense attack than the other cultivars, and the resulting smaller galls were more effectively exploited by parasitoids.

Local-scale dispersal patterns and susceptibility to Dryocosmus kuriphilus in different Castanea species and hybrid clones: insights from a field trial

“…'Pugnenga' and 'Savoye') (Sartor et al 2015), although several less susceptible varieties have been described (e.g. Sartor et al 2009Sartor et al , 2015Pérez-Otero et al 2017;Míguez-Soto et al 2018;Nugnes et al 2018;Bracalini et al 2019).…”

Assessing the Genetic Variability of Sweet Chestnut Varieties from the Tuscan Apennine Mountains (Italy)

“…In this context, their application in C. sativa germplasm has already been developed, leading to the genetic characterization of several varieties in the whole of Europe [3,[39][40][41][42][43]. Specifically, SSR markers have been previously used to elucidate the relationships among European and Italian chestnut varieties [5,[44][45][46][47] and assess the genetic diversity of cultivars and accessions across Italy, spanning from the southern to northern regions [15,19,[48][49][50]. These investigations allowed for the identification of redundant accessions, homonyms, synonyms, and intra-varietal clones.…”

“…Notably, the varietal panorama of Italian chestnuts is quite complex, encompassing numerous traditional dominant cultivars derived from the selection of a vast array of native ecotypes that have adapted to diverse geographic regions. Particularly in Central Italy, the application of SSR markers has enabled the accurate identification of predominant varieties from the Tuscan-Emilian Apennines area [19,48,49]. Alessandri et al [49] examined the genetic diversity of 134 C. sativa accessions in the Emilia-Romagna region, establishing guidelines for the characterization and varietal certification of chestnut varieties in that specific area.…”

“…It has very high productivity, and the skin peels well, making it suitable for baking and it is also used for flour. In addition, the cultivar is highly resistant and adaptable to adverse conditions [61] and less susceptible to attacks from the chestnut gall wasp when compared to Carpinese and Pastinese [48].…”