Christiane E. Helbig

This study focused on elucidating the possibilities of improving current trapping methods for Ips typographus (Linnaeus, 1758). Three field experiments were conducted simultaneously in one study area in the German federal state of Saxony. A comparison of six different commercial attractants revealed a significant superiority of Typosan^®, especially for adult beetles after hibernation in the phase of their first swarming. It also attracted fewer individuals of Thanasimus spp. than the other highly attractive products Pheroprax^® and IT Ecolure Extra^®. Increasing the Pheroprax^® application rate by using four instead of one dispenser in a single trap increased the total catch of I. typographus only by 15.5%. In contrast, Thanasimus spp. catch increased by 195.5% when four dispensers were used. A test of different trap types showed a species-specific catching capability, with the 12-funnel WitaTrap^® being the most effective in catching I. typographus. The quantity of Thanasimus spp. bycatch in multiple-funnel traps demonstrated the necessity of a selective mechanism to minimize impacts on predator populations. Although we were not able to identify new milestones towards mass trapping, this study contributes to necessary improvements of current trapping methods. Especially in future stands with a smaller share of Norway spruce (Picea abies Karsten, 1881) the weakened beetle population in spring could be effectively reduced by properly conducted mass trapping.

The cultivation of fast-growing tree species in short rotation coppices has gained popularity in Germany in recent years. The resilience of these coppices to phyllophagous pest organisms is crucial for their profitable management, since the loss of a single annual increment can lead to uncompensable economic losses. To study the effects of leaf loss on the growth of poplar and willow varieties that are frequently cultivated under local conditions, three sample short rotation coppices including five poplar (Populus spp.) and three willow (Salix spp.) varieties were established in a randomized block design with four artificial defoliation variants and, on one site, with three different variants regarding the number of defoliation treatments. After up to three defoliation treatments within two growing seasons, the results show negative effects of leaf loss on the height growth and the fresh weight of the aboveground biomass of plants. Our data also suggests a lasting effect of defoliation on plant growth and re-growth after the end of the treatment. In general, defoliation had a greater impact on the growth of poplars than on willows. We conclude that even minor leaf loss can have an impact on plant growth but that the actual effects of defoliation clearly depend on the site, tree species, and variety as well as the extent and number of defoliations, which determine the ability of plants for compensatory growth.