Grygor'yev V. Parasitic nematodes of sugar beet agrocoenoses and methods of control of their abundance under conditions of the Central part of the Forest-steppe zone of Ukraine

The thesis deals with studying the nematode fauna of sugar beet rhizosphere in the Central part of the Forest-steppe zone of Ukraine and analysis of eco-trophic belonging of the species found. A high degree of similarity of parasitic phytonematodes in agrocoenoses with different duration of sugar beet growing was established. Dynamics of abundance of nematode species and ecogroups during the crop vegetation was analyzed; it proved to depend on three interconnected factors, namely: on the period of the crop vegetation, duration of sugar beet cultivation on the same place and the year weather conditions. It is shown that phytoparasitic nematodes influence the development of sugar beet diseases, such as black leg and Cercospora leaf spot, increasing their incidence and intensity. By applying correlation and regression analyses, the dependence between the loss of root yields of sugar beet and initial abundance of beet nematodes was revealed; and the economic threshold of harmfulness of this parasite when treating beet seeds with insecticides and their compositions was calculated. The efficiency of the use of insecticides and their compositions for treatment of sugar beet seed against phytonematodes was studied, and economic evaluation of their use was given.