In this work we deal with the impact of the state of forest and bioclimatic conditions on the distribution of spruce bark beetle. With the example of larch bark beetle we have pointed out the importance of climatic conditions to the ontogenetic development of spruce bark beetle. We have determined how temperature influences the individual development stages of larch bark beetle. And at what boundary temperature the development of the individual stages to an adult begins. We also have pointed out methods of care for gradation (insect outbreaking) of larch bark beetle and usage of phenological models for determination of number of generations of larch bark beetle. Goals of this work are to familiarize with the bionomy of the most widespread larch pests. To determine the amount of caused damages in Slovakia and expected development of damages in the future with the emphasis on North Slovakia and also to determine the sense of the state of forest, which has the direct impact on spruce bark beetle gradation.