Monitoring native non-target Lepidoptera for three years following a high dose and volume application of<i>Bacillus thuringiensis</i>subsp.<i>kurstaki</i>

Boulton, T. J. C.; Otvos, IS

doi:10.1080/09670870412331286058

Cited by 10 publications

(9 citation statements)

References 25 publications

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“…As is typically the case with baculoviruses of forest insects, however, Gypchek plays only a modest role in gypsy moth control, because production costs are lower for the insecticide “Btk”, a Lepidopteran-specific bacterial toxin. Because Btk targets effectively all Lepidoptera, however, concerns over its environmental costs have led to increasing public demand for Gypchek use (Boulton and Otvos 2004; Narciso 2014; Nolan 2015). Baculovirus spray products like Gypchek may therefore be used repeatedly in the future, which may alter insect outbreak cycles.…”

Section: Discussionmentioning

confidence: 99%

Eco-evolutionary theory and insect outbreaks

Páez

Dukić

Dushoff

et al. 2016

Preprint

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Eco-evolutionary theory argues that population cycles in consumer-resource interactions are partly driven by natural selection, such that changes in densities and changes in trait values 3 are mutually reinforcing. Evidence that this theory explains cycles in nature, however, is almost nonexistent. Experimental tests of model predictions are almost always impossible because of the long time scales over which cycles occur, but for most organisms, even tests of model assump-6 tions are logistically impractical. For insect baculoviruses in contrast, tests of model assumptions are straightforward, and baculoviruses often drive outbreaks of forest-defoliating insects, as in the gypsy moth that we study here. We therefore used field experiments with the gypsy moth 9 baculovirus to test two key assumptions of eco-evolutionary models of host-pathogen population cycles, that reduced host infection risk is heritable and costly. Our experiments confirm the two assumptions, and inserting parameters estimated from our data into the models gives cy-12 cles closely resembling gypsy moth outbreak cycles in North America, whereas standard models predict unrealistic stable equilibria. Our work shows that eco-evolutionary models are useful for explaining outbreaks of forest insect defoliators, while widespread observations of intense 15 selection imposed by natural enemies on defoliators, and frequent laboratory observations of heritable and costly resistance in defoliators, suggest that eco-evolutionary dynamics may play a general role in defoliator outbreaks. 18 only infection risk given exposure (Altizer et al. 2003). Previous work has therefore not provided 45 robust tests of model assumptions.An underlying problem is that overall infection risk is best measured in the field, but for most host-pathogen interactions, field experiments are impractical. Meanwhile, for the few host-48 pathogen interactions for which experiments have measured infection risk in the laboratory or the greenhouse (Auld et al. 2014, 2013; Henter and Via 1995; Herzog et al. 2007; Zbinden et al. 2008), there are no data demonstrating that population cycles occur in nature. For insect bac-51 uloviruses in contrast, field experiments are straightforward (Elderd 2013), and because of the economic importance of the gypsy moth as an outbreaking forest pest, there are extensive data documenting gypsy moth population cycles (Johnson et al. 2005). 54Previous efforts to explain these cycles, however, have met with limited success. Classical insect-pathogen models require variability in host infection risk to prevent pathogen extinction, but realistically high variability causes the models to produce a stable equilibrium instead of 57 cycles (Dwyer et al. 2000). Extending classical models to allow pathogen transmission to be affected by induced plant defenses leads to models that can explain gypsy moth cycles, but the resulting host-pathogen/induced-defense models require particular spatial configurations of tree 60 species (Elderd et al. 2013), and so cannot explai...

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Section: Discussionmentioning

confidence: 99%

Eco-evolutionary theory and insect outbreaks

Páez

Dukić

Dushoff

et al. 2016

Preprint

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“…Pathogens are applied in very large numbers with the expectation that they will not establish, and as far as we know they do not, also indicating that their environmental risk is low. Transient effects are possible as nontarget insects will be swamped with a density of pathogen that might well be above endemic levels in the environment, potentially endangering local populations of vulnerable species (e.g., Boulton and Otvos 2004 ); but as far as we are aware, there is no evidence that they become established in these species. There are also no reports of the entomopathogens that have been released as classical biological control agents causing any negative, long-term effects; however, post-release monitoring is rare ( Hajek et al 2007 ).…”

Section: The Impact Of Genotype × Environment Interactionsmentioning

confidence: 99%

Evolution and the microbial control of insects

Cory

Franklin

2012

Evolutionary Applications

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Insect pathogens can be utilized in a variety of pest management approaches, from inundative release to augmentation and classical biological control, and microevolution and the consideration of evolutionary principles can potentially influence the success of all these strategies. Considerable diversity exists in natural entomopathogen populations and this diversity can be either beneficial or detrimental for pest suppression, depending on the pathogen and its mode of competition, and this should be considered in the selection of isolates for biological control. Target hosts can exhibit considerable variation in their susceptibility to entomopathogens, and cases of field-evolved resistance have been documented for Bacillus thuringiensis and baculoviruses. Strong selection, limited pathogen diversity, reduced gene flow, and host plant chemistry are linked to cases of resistance and should be considered when developing resistance management strategies. Pre- and post-release monitoring of microbial control programs have received little attention; however, to date there have been no reports of host-range evolution or long-term negative effects on nontarget hosts. Comparative analyses of pathogen population structure, virulence, and host resistance over time are required to elucidate the evolutionary dynamics of microbial control systems.

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“…In response, the British Columbia Ministry of Forests conducted an eradication campaign during the spring of 1999 that consisted of three aerial applications of Btk (Foray 48B®, Valent Biosciences, Libertyville, IL, USA) at 50 billion international units [BIU] in 4.0L/ha). Although Btk is an attractive alternative to broad‐spectrum synthetic insecticides, many lepidopterans are known to be physiologically susceptible to Btk formulations [8–11], and several field studies have demonstrated that aerial spraying of Btk is generally harmful to nontarget Lepidoptera in the short term [12–17]. Thus, concerns were raised by some scientists and some members of the general public that the 1999 gypsy moth eradication program on southern Vancouver Island would be harmful, at least in the short term, to susceptible native lepidopteran species.…”

Section: Introductionmentioning

confidence: 99%

“…However, a separate study [19] found no evidence to suggest that the observed reduction of caterpillars in Garry oak habitat led to a subsequent decline of songbirds (tertiary consumers, such as Cooper's hawk, were not studied). Moreover, with short generation times and high fecundity and vagility, many lepidopteran species may recover relatively quickly through reproduction and/or immigration from adjacent unsprayed habitats [17,20–22]. Therefore, assessing recovery is a vital component of pesticide impact assessment, and it is the purpose of the present paper.…”

Section: Introductionmentioning

confidence: 99%

Recovery of nontarget Lepidoptera on Vancouver Island, Canada: One and four years after a gypsy moth eradication program

Boulton

Otvos

Halwas³

et al. 2007

Enviro Toxic and Chemistry

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The gypsy moth (Lymantria dispar) is a destructive defoliator that is not established in British Columbia, Canada, because of successful eradication programs involving the microbial insecticide Bacillus thuringiensis var. kurstaki (Btk). In 1999, three aerial applications of Btk were made over two areas, totaling 12,805 ha, on southern Vancouver Island, Canada. The impacts of these Btk applications on nontarget Lepidoptera were studied from 1999 to 2004 on Garry oak (Quercus garryana) and common snowberry (Symphoricarpos albus). In 1999, lepidopteran larvae were collected from S. albus foliage at 24 urban parks and from Q. garryana foliage at 28 oak-dominated habitats. The initial impacts (i.e., 1999 data) were published previously, and the present paper is a continuation of the same study. We tested two hypotheses: Reductions of nontarget Lepidoptera would be more severe at 12 to 13 months postspray than at one to two months postspray, and recovery would be significant, though not necessarily complete, at four years postspray. The total number of nontarget Lepidoptera on S. albus and Q. garryana was significantly reduced in the treatment sites in each year of the study: the reduction was greatest in 2000. Relative to the reference sites, each of 11 species that were initially reduced by the Btk applications showed an increase in the treatment sites between 2000 and 2003, by which time only four species remained significantly reduced in the treatment sites. The uncommon species were significantly reduced in 1999 and 2000 but not in 2003, indicating that some recovery had occurred. Limitations and economic implications of the present study are discussed.

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Monitoring native non-target Lepidoptera for three years following a high dose and volume application ofBacillus thuringiensissubsp.kurstaki

Cited by 10 publications

References 25 publications

Eco-evolutionary theory and insect outbreaks

Eco-evolutionary theory and insect outbreaks

Evolution and the microbial control of insects

Recovery of nontarget Lepidoptera on Vancouver Island, Canada: One and four years after a gypsy moth eradication program

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