This master of science thesis is focused on investigation the population condition of wych elm (Ulmus glabra) and degree of tracheomycosic injury by Dutch elm disease (Ophiostoma novo-ulmi). Like experimental areas was choosen model areas with appearance of wych elm. It was Istebnianska valley in The Malá Fatra National Park and Brestova ráztoka in Kysuce Protected Landscape Area. Degree of the defoliation and damage of the elms by Dutch elm disease was evaluate from a health point of view. The significant differences between locations were not found with statistical comparation of basic dendrometrical parameters like height, pectoral thickness and projection of the crowns. However, high number of elms individuals in Brestova raztoka was characterized by lower level of defoliation and depigmentation of leaf area and therefore they had the better health condition like at Istebnianska valley. The presence of Ophistoma novo-ulmi hyphae in vessels of wood branches was identified and confirmed with electron microscopy scanning. These were previously investigated and evaluated from surface by direct observation and measurement of basic dendrometric quantities. The thesis also deals with possibilities of protecting and treating elms already suffering from various clinical symptoms of Dutch elm disease and at the same time, it explores the possibilities of eliminating propagation of elm bark beetles - Scolytus.