Occurrence, Biology and Harmfulness of Byctiscus betulae (L.) (Coleoptera, Rhynchitidae)

Abstract

In 2012 and 2013, was studied the occurrence, biology and harmfulness ofByctiscus 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 onFagus sylvatica,Tiliaspp. (namely onT. cordata),Salix capreaandPopulus 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) cm2of leaves. The females create leaf rolls on annual shoots they have gnawed, exceptionally (in 2%) on leaves with damaged petioles. In the rolls onF. sylvatica, they roll on average 5.6 leaves whose total average area is 49.5 cm2and lay on average 5.1 eggs. In the rolls onTiliaspp., they roll on average 3.3 leaves whose total area is 63.2 cm2and lay on average 4.9 eggs. In the rolls onS. caprea, they roll on average 3.3 leaves whose total area is 38.3 cm2and lay on average 3.5 eggs. The maximum number of laid eggs (on average 8.0) was observed in the leaf rolls onVitis 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. OnP. tremula,S. capreaandPyrus pyrasterthey create about 15 leaf rolls, onF. sylvaticaandTiliaspp. about 10 leaf rolls and onV. viniferaca. 8 leaf rolls. Embryogenesis lasts from 8 to 9 days. Larvae develop over 3 instars and damage ca. 300 mm2of leaves. Coming of age within 4−7 weeks, they leave the leaf rolls from mid-June to the beginning of September.