BIOLOGY OF BYCTISCUS POPULI (L.) (COLEOPTERA, ATTELABIDAE). PART II. LEAFROLLS, LARVAE AND THIS YEAR’S IMAGOES.

In 2007 to 2009, the biology of Byctiscus populi (L.) was studied on Populus tremula in Forest District B?lovice nad Svitavou (former district of Brno-venkov). Females of B. populi o en stick ends of shoots in addition to petioles in May and in the fi rst half of June. At 38% damaged shoots, they make rolls of more (at the most 4) leaves. From mid-June to the end of July, they bite only into petioles and make rolls of one leaf. The leafrolls are on average 30 mm long and 3 mm wide. With the increase of the number of rolled up leaves their mean size decreases. With the size of leafrolls the number of eggs increases. The development of eggs and larvae in leafrolls takes 26 to 38 days (in the laboratory 17 to 23 days). Larvae of the 1st instar damage on average 0.06 cm2, larvae of the 2nd instar 0.4 cm2 and larvae of the 3rd instar 2.1 cm2. Under favourable conditions, young beetles appear on trees from 15 August to 10 October. Under cold weather (2009), only part of the beetles leaves pupal chambers, namely from 10 September to 8 October. Before the beginning of a winter diapause, beetles damaged about 11 cm2 leaves of P. tremula.1