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Two efficient, semi-automatic elutriators for assaying soil samples for nematodes are described. The first apparatus is a four-unit elutriator which combines conventional extraction methods with the following major features: automatic mixing of 500- to 1,500-cm(3) soil samples with water (+/- air); "turbinate" sample splitters from which fractions of 1/15 or greater are passed onto 26- or 38-microm sieves for collection of larvae and adult nematodes; the capacity for collecting roots, intact egg masses, and cysts on 250-425-microm sieves; and a variable speed motorized sieve-shaker. Nematodes, after being collected on 38-microm sieves, are separated from debris by centrifugation or by Baermann trays. Secondary features include: air cylinders, solenoid valves, and time clock for automatic dumping residual soil and water; relay-controlled coarse spray nozzles activated for 5 sec every 30 sec for washing nematodes through 250-425-mum sieves; adjustable rates of water amt air flow, and tinting. The second type of elutriator operates on similar principles but costs less to construct. It requires somewhat more operator participation; sieve spraying is carried out by the operator, anti elutriators are dumped manually. Both elutriators also show promise for monitoring populations of certain other soil microorganisms.

A procedure for extracting eggs of Meloidogyne spp. from soil was developed by modifying and combining certain existing techniques. Egg masses were elutriated from the soft, gelatinous matrices of the egg masses were dissolved, and the dispersed eggs were stained to facilitate counting. Data on egg population densities thus obtained facilitate the study of population dynamics of Meloidogyne spp. and the analysis of root-knot epidemics.