Seguimiento de los daños de Dryocosmus kuriphilus y del nivel de control biológico causado por Torymus sinensis y otros parasitoides nativos en castaños de Navarra

The chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), is considered one of the world's greatest threats to chestnut cultivation, as it causes fruit production loss, defoliation, and canopy decline. The use of Torymus sinensis, a parasitoid, as a biological control method has been implemented in countries such as Italy, France, and several autonomous communities in Spain, while in the Foral Community of Navarre, no releases of Torymus sinensis have been carried out. However, this study has confirmed its presence, and more importantly, its expansion throughout Navarre, with significant parasitism rates. In order to monitor the evolution of the infestation by Dryocosmus kuriphilus and the effectiveness of biological control using Torymus sinensis, follow-up studies have been conducted since 2016 in a set of chestnut plots. Despite the decrease in the presence of D. kuriphilus galls, no improvements have been observed in the tree canopy density. Regarding parasitism, T. sinensis has been shown to be effective, reaching parasitism rates of 42.51% in 2020 and stabilizing at 20% in subsequent years. Additionally, the infestation by D. kuriphilus has shown a reduction to intermediate levels since its peak in 2019, with this success being mainly attributed to T. sinensis.