Occurrence, biology and harmfulness of Byctiscus betulae (L.) (Coleoptera, Rhynchitidae)

Abstract

In 2012 and 2013, was studied the occurrence, biology and harmfulness of Byctiscus betulae (L.) (Rhynchitidae) on forest woody plants in the Brno region. Leaf rolls were found on 13 species (and 10 genera) of woody plants. Most frequently, they occurred on Fagus sylvatica, Tilia spp. (namely on T. cordata), Salix caprea and Populus tremula. The beetles hibernate in ground pupal chambers and appear on woody plants in the last decade of April. After hibernation, females live on average seven (males five) weeks, and damage on average 40 (males 25) cm2 of leaves. The females create leaf rolls on annual shoots they have gnawed, exceptionally (in 2%) on leaves with damaged petioles. In the rolls on F. sylvatica, they roll on average 5.6 leaves whose total average area is 49.5 cm2 and lay on average 5.1 eggs. In the rolls on Tilia spp., they roll on average 3.3 leaves whose total area is 63.2 cm2 and lay on average 4.9 eggs. In the rolls on S. caprea, they roll on average 3.3 leaves whose total area is 38.3 cm2 and lay on average 3.5 eggs. The maximum number of laid eggs (on average 8.0) was observed in the leaf rolls on Vitis vinifera. The average number of eggs in the leaf rolls was decreasing from May to July. The number of eggs was increasing with the increasing total leaf area rolled. The females lay on average 50 eggs. On P. tremula, S. caprea and Pyrus pyraster they create about 15 leaf rolls, on F. sylvatica and Tilia spp. about 10 leaf rolls and on V. vinifera ca. 8 leaf rolls. Embryogenesis lasts from 8 to 9 days. Larvae develop over 3 instars and damage ca. 300 mm2 of leaves. Coming of age within 4-7 weeks, they leave the leaf rolls from mid-June to the beginning of September.