It has been demonstrated that pheromonal traps applied to different agricultural crops can monitor the development of populations of fleas Mamestra brassicae, Heliothis armigera, Agrothis segetum, and inform about the population density, the number of generations and the peaks of activity in each generation. It was appreciated that the species with the most plastic biological potential to adapt to the changing environmental conditions is Heliothis armigera, which surpasses the Agrotis segetum species by about 10% after the competition activity in the case when both species live on one and the same agricultural lot.