Příspěvek k poznání mandelinky Gonioctena (= Phytodecta) quinquepunctata F. (Chrysomelidae, Coleoptera)

J. Urban


Urban, J.: A contribution to the knowledge of a chrysomelid beetle Gonioctena (=Phytodecta) quinquepunctata F. (Chrysomelidae, Coleoptera). Acta univ. agric. et silvic. Mendel. Brun. (Brno), 1998, XLVI, No. 1, pp.: 7–23

In 1995–1997, a surprising gradation occurred of a little known chrysomelid Gonioctena quinquepunctata F. on rowan (Sorbus aucuparia L.) in the Polnička and Škrdlovice Forest Districts (Dr. R. Kinský Forest Enterprise, Žďár n. S.). Its mass outbreak was found on young rowan of natural seeding origin in Norway spruce plantations and on undergrowth shrubby rowan in open intermediate spruce stands. Weevils Phyllobius arborator Hbst. and Strophosoma melanogrammum Först. significantly participated in the heavy feeding and even total defoliation associated with frequent dieback of rowan. The paper deals with the size and colour variability of the beetles and particularly occurrence, development and harmfulness of the chrysomelid beetles and larvae. Males of the chrysomelid are on average 0.63 mm shorter than females. Their abdomen is usually (98 %) pale while in their females is black (90 %). In addition to the nominotypic form, the following aberrations occurred in the localities under study: unicolor Wse., nigriventris Pen., flavicollis Dft., and sorbi Wes. Last year's beetles leave their winter sites at the end of April and at the beginning of June. Ovoviviparous and viviparous females lay their eggs with quite developed embryos or egg larvae on the abaxial face of leaves as early as after some days of intensive feeding on freshly flushed leaves. The fecundity of females is very small (about 25 eggs). The development of the chrysomelid from oviposition up to the departure of mature larvae into the ground for pupation lasts in the open 3 weeks and in the laboratory 11 to 12 days. The feeding of larvae culminates usually in mid-June. The stage of pupa takes about 10 (in the laboratory 6–7) days. Young beetles of the chrysomelid occur on trees from mid-June to the end of August, more rarely up to the beginning of October. While last year's beetles die in the course of the growing season this year's beetles (after undergoing the maturation feeding) overwinter and reproduce as late as in the spring of the next year. Part of the population (1–4 %) of last year's (and to a smaller extent also this year's) beetles is killed by insect endoparasitoids (mostly Medina luctuosa Meig.). Last year's beetles, larvae and this year's beetles damage on average 580, 300 and 650 mm² of rowan leaves, respectively. The most serious damage for host trees is caused by feeding carried out in the first half of the growing season.
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