Occurrence, bionomics and harmfulness of Chrysomela populi L. (Coleoptera, Chrysomelidae)

In 2003 to 2005, Chrysomela populi L. gradated on yearly cut Populus nigra var. italica in street alleys in Brno and elsewhere. Imagoes occurred on trees from the end of April or from the beginning of May. In rearing, the chrysomelid consumed unwillingly leaves of 2-year shoots and laid on average 142 eggs. On leaves of shoots, imagoes damaged 100 to 200 cm2 during 5 to 7 weeks, produced 480 to 900 frass pellets and laid on average 506 eggs. Oviposition was continual with breaks amounting to on average 2.6 days. Embryonal development took 6 to 8 (in the laboratory 5) days. Larvae of the 1st generation occurred from mid-May to mid-July. In the course of 2 weeks (in the laboratory during 10 days) of life, they damaged about 20 cm2 leaves and produced about 300 frass pallets. In the laboratory, prepupae took 2 days and pupae 4 days. Imagoes of the 1st generation occurred from June to September. They damaged on average 113 cm2 and produced on average 553 frass pellets and 653 eggs. At a temperature of 24 to 28°C, imagoes damaged on average 84 cm2 during 2 to 3 weeks and diapaused until the next year. On growing up leaves, imagoes lived longer showing higher consumption of food and higher fecundity as against new fully-grown leaves. Larvae of the 2nd generation destroyed on average 2 cm2 smaller area than larvae of the 1st generation. Part or all imagoes of the 2nd generation diapaused. Imagoes of the 3rd generation damaged 40 to 70 cm2 leaves before departure to wintering grounds. In our natural conditions, the prospective 3rd generation is always incomplete. Cleonice callida Meig. and Schizonotus sieboldi (Ratz.) rank among important enemies.