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Nematodes of the genus Phasmarhabditis (Nematoda: Rhabditidae) are world-wide distributed molluscs´ parasites. Species P. hermaphrodita is the only commercially produced bio-agent for slug control. The aim of this thesis is to evaluate some ecologic characteristics of three newly described species of the genus Phasmarhabditis (P. bohemica, P. bonaquaense a P. apuliae) in polyxenic and monoxenic cultures. Three bacterial isolates, Pseudomonas sp., Acinetobacter sp. and Flavobacterium sp. were chosen for testing the monoxenic cultures. The growing ability of tested nematodes, the effect on the quality of progeny and the rate of development were examined on various organic substrates (compost, faeces of Deroceras slugs, homogenized Deroceras slugs, homogenized larvae of Galleria mellonella and homogenized pig kidney). Subsequently, the growth of nematodes was tested in solid and liquid media. The last experiment was focused on evaluating the impact of polyxenic and monoxenic nematode cultures on the mortality and feeding activity of Deroceras reticulatum and Cepaea hortensis. As is assumed in the results chapter, all examined species of nematodes are lethal facultative parasites of Deroceras spp. They are able to grow in broad spectre of organic substrates and bacteria which influence the production of the progeny, but the qualitative parameters of dauer juveniles remain more or less unaffected.

<p>  </p> <p>Several plant-parasitic nematode (PPN) species cause decline in the health of creeping bentgrass putting greens. PPNs target and parasitize the root systems of turfgrass which may exacerbate the impact of other biotic and abiotic stress. Turfgrass managers often apply nematicides preventatively or curatively to control PPN populations. However, the inherent chemistries of the nematicides may inhibit their ability to permeate through the thatch layer and soil, resulting in an ineffective application. This research aimed to evaluate the depth of PPN populations through the growing season to maximize the effectiveness of nematicide applications, with a primary focus on lance (<em>Hoplolaimus</em> spp.) and root-knot nematodes (<em>Meloidogyne</em> spp.). To determine the depth of genera across time, soil samples were taken with a 1.9 cm diameter soil probe to a depth of 25 cm during the months of April, June, August, and October at 7 sites across Missouri, three in eastern Kansas and ten sites in Indiana in 2021 and 2022, respectively. Significant interactions occurred between sampling depth and month in both Missouri and Indiana for some PPN genera. Additionally, individual lance and root-knot nematode species obtained from sampling were characterized with molecular methods and in the case with one lance nematode from Indiana, with scanning-electron microscopy. Results suggest an over-representation of <em>H. galeatus</em> in diagnostic literature, and a diverse collection of <em>Meloidogyne</em> spp. present in Indiana on golf course putting greens. </p>