Usefulness of egg assays in nematode population-density determinations.

Much progress has been made in developing techniques for characterizing population dynamics of nematodes. Nevertheless, most assay procedures have numerous inherent limitations (1,13). The efficiency of given methods may be dependent on soil type, moisture, and other environmental and biological factors (1,13). Certain extraction methods (e.g., Baermann funnel) depend on nematode motility. In addition, the motility of juveniles of nematodes such as Meloiclogyne javanica (Treub) Chitwood may not be correlated with infectivity (12). These problems can be overcome sometimes through bioassays (1,8,10). The precision in detecting changes in nematode populations over time can be enhanced greatly by determining egg numbers along with other life stages of these organisms (11). Numbers of eggs in cysts of Globodera rostochiensis (Wollenweber) Behrens have long been utilized in the study of this important pathogen (9). The same method is also suitable for Heterodera spp. Procedures for egg assays of Meloidogyne species and other nematodes have been developed more recently (1-4,6). Eggs of