Comparison of methods of assessing field populations of Heterodera schachtii

Abstract

Population assessment methods for Heterodera schachtü were compared in two tests. In the first there were no consistent differences between numbers of H. schachrü extracted by Fenwick cans (at two laboratories), a flotation column and an automatic cyst extraction apparatus, from dried soils from three sites containing no other cyst nematodes. The second, made on 54 commercial sugar beet fields, compared numbers of H. schachtü extracted from dried soil samples by Fenwick cans (at two laboratories) with results of a bioassay of soil samples and a subsequent examination of roots in the field. Most samples were placed into the same broad groups by the cyst extraction and bioassay methods and the two techniques were equally good at predicting field infestations.

A Fluidizing Column for Extracting Cysts of Heterodera avenae from Soil

“…nonautomated extraction methods for soils which had been stored for up to several years prior to being processed. The fluidizing column was superior to the Fenwick can and the flask methods for extractions of cysts from a newly collected soil that contained a higher density of recently produced cysts, as was reported previously (4,11,26).…”

“…Columns used in European laboratories (4,11,26) were each constructed with a transparent cylindrical column that allowed the operator to adjust the rate of water injection to achieve a visually optimal level of suspension and stirring for each soil. The column used in these experiments was constructed with opaque materials that prevented direct observation of floatation of soil particles above the fluidizing plate in the base of the column.…”

“…The flask method was particularly inefficient for extracting cysts from silty soils (11). Cooke et al (4) reported that the fluidizing method provided slightly greater extraction efficiency than the Fenwick can and the Oostenbrink automated elutriator apparatus when extracting cysts of H. schachtii from soil.…”

“…Trudgill et al (26) concluded that their method "obviously is advantageous where only limited facilities are available." The fluidizing column method of extracting Heteroderid cysts was used successfully in several leading European laboratories during the 1970s and 1980s (4,13,15,16), and an improved version at Rothamstead Experimental Station is shown in Hooper and Evans (8). Kerry (11) reported that that the fluidizing column was more effective than a combination of the Fenwick can plus an elutriation step for extracting cysts from wet and dry silt loams.…”

Impact of soil suppressiveness on various population densities of Heterodera schachtii

“…and Globodera spp. determine how many nematodes develop on a susceptible crop under controlled greenhouse conditions, but have restricted capabilities for detecting quantitative differences of soil infestation levels (Behringer, 1967;Hirling, 1970;Simon, 1980;Cooke, Mathias, Chwarszcynska & Coppock, 1983;Brown, 1987;Müller, Steudel & Schlang, 1990). Further research would be needed to determine if a tolerance limit (Ferris, 1981) can be established on the basis of the numbers of J2 at planting below which no plant damage would be expected.…”