An Assessment of the Role of Parasites and Predators in the Regulation of Cyst Nematode Populations

Abstract

Cyst nematodes have four distinct phases during their life cycle and at each stage they are subject to predation or parasitism by several soil organisms (Table 1). Although a number of predators have been observed to feed on cyst nematode eggs, second-stage juveniles, males and females, they tend to be non-specific and attack all nematodes in soil. Many of these organisms frequently occur together, are common in agricultural soils and are often numerous, but there is little evidence that they have any significant effect on the numbers of a particular pest species. Such nonspecific control is difficult to measure and exploit and consequently little research has been done to demonstrate the effects of predation on nematode populations (Esser and Sobers, 1964; Sayre, 1971; Mankau, 1980). Arthropod predators tend to be confined to the upper layers of soil and are too large to pursue nematodes through narrow soil pores. More information is needed on factors affecting the activity of predators in soil if only to ensure that agricultural practices do not remove any beneficial effects that may be occurring. Research on the biological control of cyst nematodes, as with other plant parasitic genera, mainly concerns microbial agents.