Parasitation of overwintering larvae of the European oak bark beetle (Scolytus intricatus Ratz.) by parasitoids

anglais. The purpose of the paper was to investigate the species composition and dominance of larval parasitoids of the European oak bark beetle (Scolytus intricatus) (Col., Scolytidae) in winter, as well as to estimate parasitation rates in dependence upon the host density and the thickness of material. Altogether 50 samples of oak branches and trunks with a thickness of 1-16 cm were analysed. There were found 3 species of braconids (Hym., Braconidae) and 3 species of chalcidoid wasps (Hym., Chalcidoidea). The chalcidoid wasp Entedon leucogramma (Hym., Entedontidae) was present in 78 % of samples and constituted 87,1 % of emerged imagoes of parasitoids. Mean parmitation rate of larvae was estimated to be 18.4-24,8 %. Samples with a mean parasitation rate of 0,1-10,0 % highly predominated. A number of parasitised larvae increased with increasing population density of larvae but percentage of parasitised larvae was decreasing. Mean parasitation rate was statistically significantly highest in samples with low population density of larvae (less than 250 larvae/square m) and with a thickness of 1-3 cm and 3-6 cm, respectively (on average 67,4 % and 36,6 %, respectively). Parasitation rates of other samples were considerably lower (on average 3,6-8,1 %).

slovaque. Cielom prace bolo zistit druhove zlozenie a zastupenie parazitoidov parazitujucich na zimujucich larvach podkornika duboveho (Scolytus intricatus), ako aj odhadnut stupen parazitacie v zavislosti od populacnej hustoty lariev podkornika a hrubky materialu. Analyzovalo sa 50 vzoriek konarov a kmenov s hrubkou 1-16 cm odobranych z dubovych porastov slt Fageto-Quercetum (lt 2302). Celkovo sa zistili 3 druhy lumcikov (Hym., Braconidae) a 3 druhy chalcidiek (Hym., Chalcidoidea). Chalcidka Entedon leucogramma (Hym., Entedontidae) bola pritomna v 78 % vzoriek a tvorila az 87,1% vylietanych imag parazitoidov. Priemerny stupen parazitacie lariev sa odhadol na 18,4-24,8 %, pricom vyrazne prevladali vzorky s priemernym stupnom parazitacie 0,1-10,0 %. So zvacsujucou sa populacnou hustotou lariev podkornika sa zvysoval pocet parazitovanych lariev, avsak percento parazitovanych lariev sa znizovalo. Priemerny stupen parazitacie bol statisticky preukazne najvyssi vo vzorkach s nizkou populacnou hustotou lariev (do 250 lariev/m2) a s hrubkou 1-3 cm, resp. 3-6 cm (v priemere 67,4 %). Na ostatnych vzorkach bol stupen parazitacie lariev vyrazne nizsi (v priemere 3,6-8,1 %).