<i> Torymus sinensis</i>: a viable management option for the biological control of <i> Dryocosmus kuriphilus</i> in Europe?

The chestnut gall wasp <i> Dryocosmus kuriphilus</i> is a global pest of chestnut (<i>Castanea</i> spp). Established as a pest in the mid-twentieth century in Japan, Korea and North America, this species was first reported in Europe in 2002. Following the successful release of a biological control agent <i>Torymus sinensis</i> in Japan, this parasitoid species has been released in Italy since 2005. Here we discuss the potential of <i>T. sinensis</i> as a viable management option for the biological control of <i>D. kuriphilus</i> in central Europe. We suggest that more consideration should be given to determining, (i) the conditions under which <i>T. sinensis</i> may attack alternative native gall wasp hosts and (ii) the likelihood of hybridization of this species with native <i>Torymus</i>. Both issues are central to predicting unassisted range expansion by released <i>T. sinensis</i>, and to assess the environmental risks associated with a more widespread release of this species in Europe.