Is the bark beetle Trypodendron laeve (Coleoptera: Curculionidae: Scolytinae) an alien pest in the Czech Republic and Poland?
Trypodendron laeve has a disjunctive distribution and was unknown until recently in most of Europe, where it is now considered by some sources to be an alien pest. The abundance of all four Trypodendron species in Europe (T. laeve, lineatum, domesticum, and signatum) was monitored with traps containing the aggregation pheromone lineatin, which attracts all four species, in 70- to 100-year-old Norway spruce stands in 10 study areas (seven in the Czech Republic and three in Poland). Pheromone-baited, black, window-slot traps (Theysohn, Germany) were deployed (1 to 5 per site) from mid-March/ early-April to late-May/early-June. Three Trypodendron species were captured (20,040 beetles). T. lineatum was the most abundant (n=16,922), followed by T. laeve (n=2,686) and T. domesticum (L.) (n=432); T. signatum was not detected. T. laeve was detected in three of seven study areas in the Czech Republic over the 3 years of monitoring. Although T. laeve had been detected in Poland during preliminary monitoring in 1988, it was not detected in the three study areas in Poland in the current study. The abundances of T. laeve males and females did not significantly differ in the Czech Republic. The abundance of T. lineatum was correlated with the abundance of T. laeve in the same traps. Although T. laeve has an extensive distribution, its abundance is generally low. Because the species is widely distributed in Europe, there is no practical reason to consider it alien pest in this region.