The resistance of hazel (Corylus avellana L.) to hazelnut weevil (Curculio nucum L., Coleoptera, Curculionidae). Part I. Evaluation of the resistance of several cultivars

Abstract

In the course of 5 year investigations (1981-1985) considerable differences were found in the resistance of 24 hazel cultivars to hazelnut weevil (<i>Curculio nucum</i> L.). The resistance was determined on the basis of the percentage of nuts damaged by larvae in the total yield. Six classes of resistance were established, from class I - very resistant cultivars, to class VI - very susceptible cultivars. In feeding experiments a positive correlation, significant at the 1% and 5% level was found between the frequency of beetle feeding on hazel fruitlets during the time of oviposition (July), and the class of resistance of cultivars; a negative correlation between these parameters was found in August, i.e. during hatching and development of larvae in the nuts. In July the beetles fed more readily and more frequently on nuts of susceptible cultivars, whereas they avoided them in August, i.e. in the period when larvae developed in many fruits of these cultivars.