The knowledge of the population dynamical characteristics of the pests fundamentally determines the success of the plant protection prognosis. In this paper we examine the possibilities of the utilization of the information about the population dynamical stability that we get from field examination data. We take into account neighbouring data pairs from data series regarding the change of insect density counted at stated intervals. Using these pairs of values – from the tendency of the absolute and relative changes – we can draw conclusion on the stability of the individual density values or on the stability of the whole dynamical pattern.