Current status of hazelnut weevil Curculio nucum L. (col.: curculionidae) in Duzce and Sakarya provinces of Turkey

Hazelnut weevil, Curculio nucum are among the insect species that damage hazelnuts. In this study, prevalence rate, adult population density and rate of perforated hazelnut caused by weevil's larvae were investigated in Duzce and Sakarya provinces. The studies were carried out in 29 hazelnut orchards at 2020 and 2021 groving seasons. The highest average prevalence rates of the pest were determined as 40% and 50% for Duzce and Sakarya provinces, respectively. On the other hand, prevalence rates reached up to 100% in some places. While the average number of adults per ten hazelnut clusters were 0.57 and 0.63 for Duzce, but these rates were determined as 0.25 and 0.64 for Sakarya at 2020 and 2021, respectively. On the basis of location, the highest average numbers of adults were determined as 1 and 2 for Duzce and Sakarya, respectively. Depending on the locations of hazelnut gardens, the highest average numbers of adults were determined as 4 and 2 for ten hazelnut clusters in Duzce and Sakarya, respectively. In the post-harvest examinations, significant fruit damage caused by the larvae was detected. While average perforated hazelnut fruit were 2.93 and 3.07% in Duzce and Sakarya in 2020, these rates increased to 5.63 and 4.36% in 2021. In order to prevent economic losses caused by the pest, in next production seasons, it is important to monitor the pest population and to keep them under control.