Entomopathogenic nematodes in the soil environment: Distributions, interactions and the influence of biotic and abiotic factors

Entomopathogenic nematodes (EPNs) in the families Steinernematidae and Heterorhabditidae are important agents for the biological control of soil insect pests in natural and managed ecosystems (Denno, Gruner, & Kaplan, 2008; Grewal, Ehlers, & Shapiro-Ilan, 2005; Lacey & Georgis, 2012). However, like most soil organisms, our knowledge of their activities is relatively limited compared to above ground organisms. Indeed, research on soil biota has long been a challenging aspect of modern ecology because of the inherent difficulties of sampling, manipulating, and otherwise investigating below ground processes (Brown & Gange, 1990; Fierer, Strickland, Liptzin, Bradford, & Cleveland, 2009). Progress is being made with EPNs but we are still a long way from the comprehensive understanding of their soil biology that is required if they are to fulfill their rich potential as manageable biological control agents in cultivated ecosystems. Twenty-five years ago Hominick and Reid (1990) stated: “We are almost completely ignorant of the population biology of entomopathogenic nematodes, yet such information is fundamental to understanding their persistence, distribution, effect on insect populations, and to the development of predictive models for control programs.” Subsequently, researchers have been chipping away at this problem, more intensive field studies have been conducted, models have been developed for various processes, and molecular techniques have begun providing new ways of exploring fundamental issues (Bai, Adams, Ciche, Clifton, Gaugler, et al., 2013; Campos-Herrera, Barbercheck, Hoy, & Stock, 2012; Campos-Herrera, Pathak, El-Borai, Stuart, Gutiérrez, et al., 2013; Stuart, Barbercheck, Grewal, Taylor, & Hoy, 2006) but much remains to be done. This paper reviews some aspects of the distribution of EPNs in the soil environment, what.