In extensive experiments during a period of 5 years we could prove that 1. the population density could not be substantially influenced by a massive and continuous mass trapping with pheromone baited traps neither of Ips ty ographus nor of Trypodendron lineatum; 2. the protection of an object by this method is in case o f t h e first-named insect possible but against the second one not; 3. the number of bark beetles on a given place is not exclusively decisive for the attack of trees; the monitoring in a certain time and the forecast based on this date have therefore a vague character; 4. there is a good correlation between the manner of forest management on the one hand and the PO ulation density of bark beetles or the number of attacked trees, respectively, on the other: the soc d e d clean-mana ement is the best, probably the most reliable and at long sight also the most reasonable methofi against the propagation and the attack of the bark beetles. MethodsIt has been proved that a great number of bark beetles can be captured by use of the three pheromonecompounds (PHEROPRAX, CHALCOPRAX and LINOPRAX) and of suitable traps (particularly the so-called three-trap-star). This fact seemed to demonstrate the applicability of the method for monitoring and prognosisi. e. we can obtain reliable dates about the begin of beetle-flight and about the aproximate density of beetle-population.