The aim of the project is the development and construction of an electronic system in the form of the device, often called electronic nose (e-NOSE), to detect a particular smell, or a mixture of different scents. For selected samples and on the basis of accumulated research material there will be presented possibilities of using this device for the measurement of degradation of the forest against pathogens and harmful insects. Pine-tree lappet is one of the most dangerous phyllophagous pests. Since 1946 she appeared in the form of a gradation 9 times. In 2013, the protective treatments against lappet were carried out on the surface of approximately 120 thousand ha. The forecasting risk by pine-tree lappet is performed mainly on the basis of an assessment of the caterpillar density accumulation for wintering in the leaf litter, by the method of the autumn searching on 10 surfaces. Complementary methods are spring rating population size by trees agglutinating and felling trees on the sheets. As a result of the existing research on the pine-tree lappet caterpillars it was found that from the time of hatching from eggs they tend to focus in the groups. The strongest tendency of caterpillars to group has been observed in the first three stages of development. The phenomenon of caterpillars’ group life is in relation with development pheromones of this species. The places where aromatic substances, causing the focusing of caterpillars, are produced are the heads. The aim of the undertaken studies, using the e-NOSE, is localization of leaf litter wintering caterpillars by elaborating new method of risk assessment of pine stands by pine-tree lappets on the basis of smell emitted in wintering places of pine-tree lappet caterpillars and on the trees after overwintering.