Entomofauna of dying young spruces Picea abies (L.) Karst. in the area after forest decline in the Izerskie Mountains

Abstract

The results of the study on entomofauna infesting young (25– 45 years) Norway spruces (Picea abies [L.] Karst.) in the area formerly affected by forest decline in the Izerskie Mountains (Western Sudetes), are presented in the paper. Entomological analyses were carried out on tree sections (0.5m long) obtained from 50 trees (3 sections each) as well as during photoeclector rearing of tree samples (28 sections 0.5m long). Bark- and wood-boring insects of 21 species and 1 genus were found. The dominant species was Pityogenes chalcographus L. (88% frequency in field analyses) usually accompanied by Ips amitinus (68%). Both species frequently infested whole stems (found in all 3 sections in 62% of analyzed trees). In the group of predators and commensals, 13 species were found, with most frequent Corticeus linearis (Fabr.), Crypturgus spp. and Medetera signaticornis (Loew.). Among the parasitoids belonging to 7 species and 4 genera, Braconids and Pteromalids known as parasites of Scolytid bark beetles, were most common. Taking into consideration reccurence of natural processes such as insect outbreaks, probability of the scenario described in the paper, i.e. shifting bark beetle attack from old into young spruce stands after Ips typographus L. outbreak, is very high in the area of current decline of the Norway spruce in the Western Carpathians.