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

Abstract

Summary1. The nematode Steinernema feltiae has been developed commercially as a biocontrol agent and is successful in controlling sciarid flies in mushroom houses. We used a simple model developed in parallel with a series of field trials, to optimize the application strategy of the nematode. 2. The first field trial provided life-history parameter estimates for both the sciarid flies and the nematodes and showed there to be substantial levels of nematode recycling, leading to high levels of control. Crucially, the field trial showed that by splitting the application into two, and applying half the nematodes at day 0 and half at day 7, the overall number of nematodes (dose) could be substantially reduced from currently recommended levels without sacrificing control success. 3. The model confirmed that there should be a benefit in splitting the dose, if the second application is timed to coincide with the peak in numbers of highly susceptible sciarid larvae. Importantly, the model provided insight into the dynamics of the sciarid larvae, even though the original data set only recorded adult fly numbers. 4. Using a split dose, optimally timed, the model suggested that total doses could be reduced by up to 75% and still achieve control comparable to that found with currently recommended dosages. The timing of the second application of nematodes was crucial in determining the level of control. 5. The model predictions were validated against a second independent field trial with considerably lower fly densities. Even under these different conditions, the predictions were accurate, indicating the robustness of the modelling approach. 6. To date models have rarely provided genuine practical advice to applied agriculturists and biocontrol practitioners. This study shows how a simple model developed in parallel with replicated field trials leads to a better understanding of the biological processes underlying successful control, resulting in improvements in recommended application strategies.

Controlling western corn rootworm larvae with entomopathogenic nematodes: effect of application techniques on plant‐scale efficacy

“…Such a granule would need to keep the EPNs alive within the granule during transport (i.e. provide adequate moisture and aeration); but at the same time would need to prevent excessive EPN activity within the granule to ensure longevity (Fenton et al. 2002).…”

Development of a model for evaluating the effects of environmental temperature and thermal behaviour on biological control of locusts and grasshoppers using pathogens

“…There has been much interest in being able to predict success and to improve effectiveness of microbial biocontrol. For example, models have been used to investigate disease dynamics ( Carruthers et al , 1988( Carruthers et al , , 1992Briggs and Godfray, 1995;Larkin et al , 1995 ), application method and factors influencing disease prevalence ( Hajek et al , 1993;Barlow et al , 2000;Scanlan et al , 2001;Fenton et al , 2002 ), to identify pathogens with the greatest potential ( Nowierski et al , 1996;Feng et al , 1998 ), and to examine short-and long-term infection patterns after spray application ( Thomas et al , 1995;Thomas et al , 1999 ). However, there has been very little attention to factors determining virulence and, to our knowledge, this is the first model that quantitatively captures variability in the speed of kill of a pathogen in different field environments.…”

How maize root volatiles affect the efficacy of entomopathogenic nematodes in controlling the western corn rootworm?

“…Apparently some early applied nematodes persisted, probably by producing a new generation on alternative hosts that resulted in sufficiently high abundance to reduce the later hatching WCR population. For inundative biological control strategies, it remains essential to find the optimal dose and release timing (Fenton et al 2002).…”