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ŠUMARSKI LIST 3-4/2014 str. 40     <-- 40 -->        PDF

The large larch bark beetle (Ips cembrae) is a secondary pest species which tends to build outbreaks in certain condition particular after drought stress or thinning. If enough suitable material is available in the forest, population density starts to grow and in lack of weakened trees the bark beetles attack healthy trees. In such circumstances this beetles are considered as primary pests. Regarding new problems with this bark beetle species in Croatia and trends of environmentally friendly forest protection measures, it is essential to determine the occurrence and possibilities of population spreading of the large larch bark beetle and gain new knowledge about possibilities for using pheromone traps against this pest.
The results are showing occurrence, distribution and damage of large larch bark beetle in Croatia. Although large larch bark beetle has been mentioned in several publications as present in Croatia, there is no provable evidence of this because no locality has ever been given neither in publications nor entomological collections. Therefore the record of large larch bark beetle in Koprivnica on European larch (Larix decidua) in October 2008, could be considered as the first record of this pest species in Croatia. The large larch bark beetle was recorded from 2008 till 2013 at 24 forest sections in 7 Forest districts, in 23–58 old stands at elevation of 160–350 a.s.l. The distribution map shows the infection spreading which amounts up to 17km yearly. For monitoring purpose pheromone traps (Theysohn®) baited with Cembräwit® were installed in 2011. The monitoring was observed trough the vegetation period from 2011 till 2013 which is the first pheromone trap monitoring of this species in Croatia. It was found that the first generation is swarming in middle April. Further only one generation was recorded till 2012 and just in 2013 a second generation occurred in August and September. The damage of this pest was assessed by number of marked trees and timber volume of felled trees. In total 4.922 larch trees were infected which is 2.121m3 timber volume. The majority of timber volume was marked for felling in 2012 and 2013 probably influenced by drought combined with high temperature and very long periods without precipitation. In such conditions larch trees were highly stressed and physiologically weakened. This was the trigger for bark beetle attack. In the coming years a further spreading to new locations in Croatia is expected.
KEY WORDS: Ips cembrae, Larix decidua, Theysohn®, Cembräwit®, pheromone trap, bionomy