Incidence of damage by nut weevil on different hazelnut cultivars in northwestern Italy

The nut weevil Curculio nucum L. (Coleoptera: Curculionidae) is one of the major hazelnut pests, responsible for high yield losses in Europe and Turkey. However, some hazelnut cultivars seem to be more resistant to the nut weevil attacks, even if mechanisms involved in the resistance are not yet altogether known. In a previous study on two cultivars and four selections of hazelnut, the susceptibility to nut weevil appeared to be related to the timing of shell hardening. Therefore, a three-year study on 15 hazelnut cultivars was carried out to assess their susceptibility to the nut weevil. In addition, nut and kernel development stages and shell hardening were detected. At harvest, nut weevil damage was significantly different between the cultivars. Despite their different earliness, ‘Hall’s Giant’, ‘Tonda di Giffoni’ and ‘Tonda Gentile delle Langhe’ were the least damaged (<5.0%), whereas the latest ‘Cosford’ showed the highest damage (35%). Thus, the earliness of nut development resulted not to be the only factor affecting the rate of nut weevil damage at harvest.