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 typographus nor of Trypodendron lineatum; 2. the protection of an object by this method is in case of the 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 population density of bark beetles or the number of attacked trees, respectively, on the other: the so-called clean-management is the best, probably the most reliable and at long sight also the most reasonable method against the propagation and the attack of the bark beetles.
