Response of Ips typographus (Scolytidae: Coleoptera) and other bark- and wood-boring beetles to a flash-flood event

On 30 - 31 August 1997, a thunderstorm accompanied by heavy rain caused flood erosion on the forest-covered slopes of Mt Fulufjall in central Sweden. Large numbers of mature Norway spruce trees [ Picea abies ( L.) Karst.] were uprooted and deposited along streams in the area. Attacks by bark- and wood-boring beetles in lying spruces were recorded along three flooded and three unflooded streams in the three years following this flooding event. The bark beetles Ips typographus ( L.), Pityogenes chalcographus ( L.), Orthotomicus sp. and the cerambycid Monochamus sp. were found to be much more abundant along flooded than unflooded streams. In contrast, the bark beetle Hylurgops glabratus (Zett.) showed the opposite pattern. Mortality among standing trees peaked in the second year following the flooding event. A considerable proportion of this additional tree mortality could be attributed to attacks by I. typographus. In contrast, no trees killed by this species were found along the three unflooded streams.