Monitoring of virus diseases of sugar beet in Slovakia.

Rhizomania, one of the most serious diseases of sugar beet is caused by bee t necrotic yellow vein furovirus (BNYVV), whose vector is the soil-borne fu ngus Polymyxa betae, a member of the Plasmodiophoromycetes. Another virus d iseases of sugar beet - sugar beet mosaic (caused by Beet mosaic potyvirus - 'BtMV) and sugar beet yellows (caused by Beet yellows closterovirus - BW or Beet mild yellowing virus - BMYV) are transmitted by more than 30 spp. i nsects. In this article there are given the results of monitoring of beet m osaic virus and beet yellows virus in ten areas of west Slovakia in 1998, t aking into account the incidence of rhizomania in these areas. The virus qu antity has been determined serologically, by the ELISA according to Clark a nd Adams (1977). Obtained results are shown in Fig. 1 and Fig. 2. These res ults provide experimental evidence that beet necrotic yellow vein virus ass ociated with rhizomania disease in sugar beets occurs in Slovakia in 43 of the 70 localities tested (in 41 localities A(405) was about 0.5, in 2 local ities A(405) was higher than 1). 27 localities were tested negative. Beet m osaic was tested positive in 3 of 10 localities (2 in Trencin county and 1 in Nitra county) and measured absorbances in ELISA were higher than 1, it m eans that disease incidence in these localities was severe. The occurrence of beet yellows was proved only in 1 of 10 localities tested (in Trencin co unty) with A405 higher than 1. Positive results for beet mosaic and beet ye llows correlated with strong incidence of aphids in these localities (Ryban y, Oponice, Trencianska Turna.). Obtained results pointed to an infestation by the virus disease rhizomania. Survey of beet mosaic (about 30 % fields were positive) and beet yellows (about 10 % fields were positive) revealed, that incidence of these diseases is lower than ten years ago when producti on fields of sugar beet seed plants were grown by the traditional technolog y of planting (Bojnansky, 1990). We believe that it is due to the new techn ology of the production of sugar beet seed through direct sowing, which led to reduction of virus diseases of yellows and mosaic type. However plant p rotection to virus diseases is permanent problem required new observations and solutions each year.