Pheromone trapping of the double-spined bark beetle Ips duplicatus (Coleoptera: Curculionidae, Scolytinae): seasonal variation in abundance

Ips duplicatus adults were sampled with pheromone-baited black window-slot traps (Theysohn) in 70- to 100-yearold Norway spruce (Picea abies) stands between 280 and 650 m a.s.l. in the eastern Czech Republic and southern Poland during 2000- 2010. Sets of 5-12 traps were placed about 20 m from the edge of the infested forest. Each trap was baited with a standard synthetic pheromone lure (ID Ecolure), and was setup 1.5-2.0 m above the ground. The objectives were to determine the relationship between the numbers of adults trapped in the overwintered generation and those in the offspring generation. According to data from 135 traps, the numbers of overwintered beetles captured in spring (April-June) were significantly higher than the numbers captured in summer (July-August), but the numbers of offspring beetles captured in summer were significantly correlated with the numbers overwintered beetles captured in spring. The spring captures can be used to estimate the threat caused by I. duplicatus during the whole vegetation season. The traps installed in summer should be used to determine the peaks in the bark beetle flight activity, thus enabling early identification of trees infested by I. duplicatus, especially inside stands.