The incidence of Pythium spp. and Aphanomyces cochlioides associated with the sugar-beet growing soils of Britain

In a survey of fungi causing seedling diseases of sugar beet using a soil bioassay, Aphanomyces cochlioides and Pythium spp. were found to occur in 39% and 31%, respectively, of 341 sugar-beet fields selected in a stratified random sample in England. The frequency of A. cochlioides-infested soils varied widely in the different sugar-beet growing areas of the country. Soil pH was the single factor most strongly associated with the distribution of the pathogen, but regression models applied to combinations of factors indicated that soil texture and the interval between sugar-beet crops were also relevant to its frequency. It was detected less often in soils of high pH (greater than or equal to 7.5), heavy texture and where the interval between sugar-beet crops exceeded 5 years. No significant associations were found between the proportion of soils with Pythium spp. and soil or cropping factors.