Distribution and harmfulness of field dodder (Cuscuta campestris Yuncker) at sugar beet fields in Slovakia

During 2002-2004, field surveys of field dodder (Cuscuta campestris Yunck e r) in croplands were done in southwestern Slovakia. From among 150 localities surveyed, 80 were found infested by the field dodder. Within crop plants, C. campestris infested sugar beet (Beta vulgaris), alfalfa (Medicago sativa) tobacco (Nicotiana tabacum), potato (Solanum tuberosum), lentil (Lens esculenta), parsley (Pastinaca sativa) and onion (Allium cepa). Besides the crops, 18 weed species were also recorded. The species from the genus Polygonum (Polygonaceae) were the most important and acted as a significant reservoir of field dodder in cropland. C. campestris was not found in cold climatic regions with altitude higher than 240 m. The impact of field dodder infestation on sugar beet yield was studied during the year of 2004 in two localities (Šalov and Žitavce) in southwestern Slovakia. The presence of field dodder markedly reduced both, quantity and quality of sugar beet yield. Weight of heavily infested beets was reduced from 21.6 to 37.4% and sugar content from 12.0 to 15.2%. Such decline of both parameters was also recorded when field dodder was removed together with leaves of sugar beet during growing season at the end of July. The aim of the infested leaves removal was to decrease mass of field dodder seeds. Although the leaf area of sugar beet regenerates, the decrease of quality and quantity was observed. The decline was the same at both localities, no matter whether the fields were irrigated (Šalov) or not (Žitavce)