EXPERIMENTS ON MONOTERPENES IN COMBINATIO N WITH PHEROPRAX(R) AND CHALCOPRAX(R) IN PHEROMONE TRAPS FOR CATCHING THE BARK BEETLES IPS-TYPOGRAPHUS L AND PITYOGENES-CHALCOGRAPHUS L (COL, SCOLYTIDAE)

Experiments on monoterpenes in combination with Pheroprax(R) and Chalc oprax(R) in pheromone traps for catching the bark beetles Ips typograp hus L. and Pityogenes chalcographus L. (Col., Scolytidae) It is highly evident that monoterpenes of the host tree serve as olfactory stimula nts for ''pioneer-beetles'' colonizing first a tree before any bark-be etle-produced aggregation pheromones can lure those beetles to the hos t. The findings of REDDEMANN (1993) about a significant increase of sp ruce engraver catches by addition of both (-)-alpha-pinen and (+)-limo nen simultaneously to pheroprax-baited bark beetle traps (Pheroprax(R) being the aggregation pheromone of Ips typographus) induced us to con duct field experiments testing the same host volatiles in comparable b ark beetle traps baited with either Pheroprax(R) or Chalcoprax(R) (agg regation pheromone of Pityogenes chalcographus). Despite we used metho ds considering the influence of place and time on the bark beetle flig ht activities, in 3 experiments with 30 repetitions in total no monote rpene-induced enhancement of typographus-catches could be found; the s ame was true with P. chalcographus (2 experiments, 18 repetitions in t otal). With respect to the important role of host volatiles also from a practical point of view, it is strongly recommended to repeat experi ments like these under different conditions to reveal the reasons of t he different findings.