Evaluating the Efficacy of Entomopathogenic Nematodes for the Biological Control of Crop Pests: A Nonequilibrium Approach

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. The University of Chicago Press andThe American Society of Naturalists are collaborating with JSTOR to digitize, preserve and extend access to The American Naturalist.http://www.jstor.org abstract: The efficacy of entomopathogenic nematodes for biological control is assessed using deterministic models. Typically, the examination of such models involves stability analyses to determine the long-term persistence of control. However, in agricultural systems, control is often needed within a single season. Hence, the transient dynamics of the systems were assessed under specific, shortterm control scenarios using stage-structured models. Analyses suggest that preemptive application may be the optimum strategy if nematode mortality rates are low; applying before pest invasion can result in greater control than applying afterward. In addition, repeated applications will suppress a pest, providing the application rate exceeds a threshold. However, the period between applications affects control success, so the economic injury level of the crop and the life history of the pest should be evaluated before deciding the strategy. In all scenarios, the most important parameter influencing control is the transmission rate. These findings are applicable to more traditional biological control agents (e.g., microparasites and parasitoids), and we recommend the approach adopted here when considering their practical use. It is concluded that it is essential to consider the specific crop and pest characteristics and the definition of control success before selecting the appropriate control strategy.Keywords: biological control, entomopathogenic nematodes, insect pathogen, nonequilibrium analysis, transient dynamics, models of intermediate complexity.Over the past 30 yr, there has built up a vast literature describing the use of models as tools to evaluate the success One aspect that has received considerable attention in the last 10 yr is the incorporation of explicit stage structuring in the insect-host population (Murdoch et al. 1987;Godfray and Waage 1991;Godfray 1995a, 1995b;Murdoch and Briggs 1996). Such stage structuring, in the form of coupled delay-differential equations, enables greater biological detail to be described by a few, intuitively defined parameters while maintaining a degree of analytical tractability.However, despite the increased realism of this new generation of models, it may be that, at least in terms of evaluating biological control success, they are not being used to address the pertinent questions. In recent years, a number of authors have drawn attention to the fact that long-term stability rarely has any bearing on the practical success of a control program (Murdoch et ...

Optimal application strategies for entomopathogenic nematodes: integrating theoretical and empirical approaches

“…Typically, the different trials, working with different nematode strains and different fly species in different growing conditions, all lead to different recommended doses. Previous theoretical work (Fenton et al . 2000, 2001) has shown that control success can be very sensitive to certain biological parameters (e.g.…”

“…Furthermore, these models enable us to include one essential feature of the sciarid fly–nematode interaction: only the larval stages of the sciarid fly are susceptible to infection. We have previously developed such a stage‐structured model, based on our earlier SI model, and used it to explore a number of specific short‐term control scenarios in a range of crop pest systems (Fenton et al . 2001).…”

The Invasion and Encapsulation of the Entomopathogenic Nematode, Steinernema abbasi, in Aedes albopictus (Diptera: Culicidae) Larvae

“…EPNs are often applied as short-term inundative biological control agents in large numbers to bring about a rapid and severe decline in pest numbers [17,23,48], but only a fraction of these successes was found in a host [17]. In addition, the susceptibility of target insects varies depending on nematode species and strains [17,30].…”

Molecular Identification and Phylogenetic Diversity of Native Entomopathogenic Nematodes, and Their Bacterial Endosymbionts, Isolated from Banana and Plantain Crops in Western Colombia

“…The infection efficiency of EPNs relies on the enhanced pathogenicity of their bacterial symbiont [31,33]. Initially, the nematode enters into the insect's body via natural openings, with a posterior release of the symbiotic bacteria into the host hemocoel, causing septic shock and killing the insect in 24-48 h [26,[38][39][40]. This enables the optimal conditions for EPNs' reproduction and multiplication before the insect's death.…”