Contribution to the knowledge on bionomics of Byctiscus betulae L. (Coleoptera, Curculionidae) on grapevine

Abstract

At a time of its massive occurrence on grapevine a less known part of the vine leaf roller (Byctiscus betulae L.) bionomics was studied in the period from the last decade of April until the first decade of May 2000 in the region of Slovenian Istria. It was established that in 90% of the cigar-like structures, which are formed of rolled leaves, their length was between 6.5 to 10.0 cm. In almost 50% of cases the females lay 3–4 eggs per 'cigar'. A statistically significant and very weak positive correlation was noted between the length of the 'cigar' and the number of eggs laid into the ‘cigar’. A similar statistical relationship was observed between the number of bitten leaves during the supplemental feeding of weevils and the number of ‘cigars’. This shows that the number of laid eggs is influenced by a number of factors and that the females do not lay eggs only on the plants on which they feed, but also on other plants. Though the weevil can harm on average more than 10 leaves in the early stage of vine development, it is listed among interesting rather than among damaging insects. The most abundant in the population were the weevils of metallic green color.