On the occurrence, bionomics and harmfulness of Chrysomela vigintipunctata in the Czech Republic
1997
Urban, J. (Mendelova Zemedelska a Lesnicka Univ., Brno (Czech Republic))
Heavy feedings to clear eatings Chrysomela vigintipunctata were found in willows Salix fragilis and S. x rubens. Other willows were damaged to a lesser extent and S. triandra (similarly like other kinds of forest tree species) was not damaged at all. It is the chrysomelid beetles that winter. In May, females lay eggs in compact groups of 39.3 pieces on average onto the abaxial face of leaves. In total, their performance is about 250 eggs. Grown-up larvae pupate mainly on the abaxial side of leaves or on the bark of drying up terminal parts of shoots. There were up to 25 pupae found on the leaves, and as many as nearly 50 were found on the shoot ends of 10 to 15 cm in length. In the open, preimaginal development takes 38 days. In the laboratory, it is 21 days. The hatched beetles pass through the stage of maturation feeding on the leaves of host tree species, which lasts approximately three weeks. As early as in the month of July, they withdraw to wintering places into shed leaves or tree slits. After wintering, the beetles damage on average 3,540 mm2 leaves of S. fragilis. The larvae of the first, second and third instars damage 34, 95 and 548 mm2, respectively, and damage by the young beetles amounts to 1,180 mm2 leaf area.
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