Risk of attack by the bark beetle Pityogenes chalcographus (L.) on living trees close to colonized felled spruce trees

The bark beetle Pityogenes chalcographus (L.) occasionally kills trees in young stands of Norway spruce Picea abies (L.) Karst. Suitable breeding material, e.g. piles of fresh logging waste, may potentially increase the risk of attacks on nearby stands. In southern Sweden, young spruce were cut and piled in spring at 31 stand edges of young spruce facing clear-cuts. Pityogenes chalcographus attacks were recorded within stand edge plots near the piles during two summers after piling. Plots randomly located along 27 stand edges without piles were used as controls. The experiment was repeated in 3 yrs. All piles were colonized by P. chalcographus early in the first summer after piling. Plots with piles had five times more attacked standing trees, and >40 times more entrance holes than controls. Almost all attacks occurred when the piles were being colonized. Of a total of 226 attacked trees only four were killed. In conclusion, the risk of P. chalcographus killing young healthy spruce trees close to piles of breeding material is low.