European spruce bark beetle causes big damage in spruce forests. According to the weather can has more than one generation during a season. Objective of this work was finding spring, summer swarming based on phenologic models. It was nessesery determination and estimating population size of IT with emphasis on the effective temperature. Throught to the work, we recognize the biomomics of IT, ist life cycle and effect, how it damages spruce stands. Within the detected population rates of damage was evaluated the damage in the Vlčovo forest. In this work is important to be aware the reproductive power and harmful potencial IT in our forests.