Plant parasitic nematodes of sugar beet fields in the territory of Slovakia

In the years 1999 and 2000 research of occurrence and distribution of plant parasitic nematodes was done in the sugar beet growing areas of the Slovak Republic (western, south-western and south-eastern part of the region). Total of 64 sugar beet fields were investigated in areas of six sugar-refineries (Dunajsk  Streda, Sered, Trnava, Rimavska Sobota, Surany a Trencianska Tepla). In July and September soil samples were collected from the rhizosphere of sugar beet (at a depth of 0.2 m) alternately from every fifth row. The average samples were obtained by mixing of ten basic samples. Nematodes were isolated from the average soil samples 500 g by the Cobb methods and fixated in FAA (Ditlevsen's solution composed of 500 ml of 95% ethanol, 100 ml of 40% formalin, 20 ml of glacial acetic acid and 400 ml of distilled water). Identified nematodes were divided into two groups - obligate and facultative plant parasitic nematodes. The following indices were used: - the extensity of occurrence of plant parasitic nematodes, expressed by percentage of positive localities from total number of investigated localities, - the occurrence and distribution of economically important species of plant parasitic nematodes, which were evaluated according to percentage proportion from the total nematodofauna in the samples as follows: 0 - 10% proportion - rare occurrence, 11 - 25% proportion - abundant occurrence, 25% proportion - massive occurrence. The most numerous as well as the most distributed genus of plant parasitic nematodes in sugar beet fields was Pratylenchus with its occurrence in 93.8% of localities. In six localities mass occurrence of this parasite was recorded. The genus Tylenchorhynchus had extensity of occurrence 92.1%, the genus Helicotylenchus 64.1%, Ditylenchus 57.8% and Heterodera schachtii juveniles were found on 15.6 percentage of localities. The most abundant population showed the genus Paratylenchus (646 individuals in 500 g soil)