Separation of cysts from the soil by decantation and centrifugal floatation technique

SHIMIZU Kei

doi:10.14855/jjn1972.8.20

For estimating Heterodera cyst population in soils, the following four methods were compared: 1. cyst floatation with Fenwick's can, 2. centrifugal floatation of the float obtained by the former method, 3. decantation of undried soil into an 80 mesh sieve, and centrifugal floatation of the remainder on the sieve, 4. the same as the third method except for using air-dried soil instead of undried soil. The soils used in the present tests were volcanic ash loam from fields infested with the upland rice cyst nematode, Heterodera elachista, and soil previously added with the cysts. Results obtained were as follows:(1) significantly higher recovery rates and lower coefficients of variability were obtained by the 2nd and the 4th method, particularly the highest rate by the latter.(2) Using hypo (sodium thiosulfate) solution (s. g. 1.40) resulted in a higher recovery rate than with tap water or sugar solution (s. g. 1.20) for the centrifugal floatation technique.(3) It is concluded that examination of supernatant obtained by centrifugal floatation with hypo solution after decantation of air-dried soil appears sufficient to secure 90% recovery, and is practical as a simple, rapid, and inexpensive technique for estimation of the cyst population.

Separation of cysts from the soil by decantation and centrifugal floatation technique

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