Native and introduced parasitoids in the biocontrol of Dryocosmus kuriphilus in Veneto (Italy)

Abstract

The invasive gallmaker Dryocosmus kuriphilus is a threat to chestnut stands and it is necessary to control it in order to maintain a satisfactory nut yield. A preliminary evaluation of the native natural enemies emerging from the galls, mainly parasitoids associated with native cynipid gallmakers, revealed that they were not able to contain the pest. Consequently, a classical biological control programme using Torymus sinensis started in 2010, with almost 500 releases being made in 6 years. The parasitoid achieved a satisfactory level of control of the pest over a period of time shorter than expected based on literature related to other countries. The success in the study area might be explained by specific traits intrinsic to T. sinensis, such as its high spread capability via stratified dispersal (i.e. a combination of short‐ and long‐distance flights), together with a large availability of host galls and limited competition with other parasitoids.

Success of classical biocontrol agent Torymus sinensis within its expanding range in Europe

“…This was also the case with T. sinensis released in Slovenia, Croatia and Hungary as the samples were collected on a few connected sites in the vicinity of Torino, Italy. On the other hand, the populations of T. sinensis in Italy have been established after several introduction events since 2005 (Quacchia et al 2008;Bosio et al 2013;MIPAAF 2016;Colombari and Battisti 2016). Thus, high diversity rates shown in this study can be attributed to extensive collecting of native parasitoid populations in Japan before their introduction to Italy (Quacchia et al 2008), and subsequent unconstrained dispersal through Italy over Slovenia to Croatia and Hungary.…”

“…Intensive releases have been made in Veneto region, Italy, since 2010 (Colombari and Battisti 2016), and T. sinensis has covered the distance crossing Slovenia to Croatia and Hungary in 4 years. This rapid dispersal of T. sinensis was aided by high concentration of the host, as well as the lack of competition of native parasitoids (Mato sevi c and Melika 2013; Kos et al 2015;Colombari and Battisti 2016) and landscape composition of connected sweet chestnut forests, wooded chestnut patches, individual chestnut trees and orchards (Medak 2009) in the investigated area. With the host D. kuriphilus present in abundance, successful mate finding and probably no major limiting factors (i.e.…”

Resistance of a Local Ecotype of Castanea sativa to Dryocosmus kuriphilus (Hymenoptera: Cynipidae) in Southern Italy

“…Due to its concealed life cycle inside the chestnut buds and galls, the management of ACGW is challenging. Moreover, although there has been a quick shift of a very rich complex of indigenous parasitoid species from oak cynipids to D. kuriphilus, their action seems to be insufficient in controlling ACGW [16][17][18][19][20]. To date, the only effective method of control has been the introduction of Torymus sinensis Kamijo (Hymenoptera: Torymidae), a parasitoid native to China [21][22][23][24]; the control effectiveness of T. sinensis reached satisfying levels after a variable number of years (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) [21,22,[24][25][26].…”

Next Generation Biological Control: The Need for Integrating Genetics and Evolution

“…This is a low-cost alternative to PCR that can be conducted in a single test tube and at a single temperature. In a biocontrol context, this method has been tested with the Asian chestnut gall wasp parasitoid Tormyus sinensis (Colombari & Battisti, 2016). It can efficiently be employed for measuring parasitisation rate in the field, especially as it can be used for juvenile stages when species identification is most difficult.…”