title: Combining pest control and resistance management: synergy of engineered insects with Bt crops.
abstract: Transgenic crops producing insecticidal toxins are widely used to control insect pests. Their benefits would be lost if resistance to the toxins became widespread in pest populations. The most widely used resistance management method is the high-dose/refuge strategy. This requires toxin-free host plants as refuges near insecticidal crops, and toxin doses intended to be sufficiently high to kill insects heterozygous for a resistant allele, thereby rendering resistance functionally recessive. We have previously shown by mathematical modeling that mass-release of harmless susceptible (toxin-sensitive) insects engineered with repressible female-specific lethality using release of insects carrying a dominant lethal ([RIDL] Oxitec Limited, United Kingdom) technology could substantially delay or reverse the spread of resistance and reduce refuge sizes. Here, we explore this proposal in depth, studying a wide range of scenarios, considering impacts on population dynamics as well as evolution of allele frequencies, comparing with releases of natural fertile susceptible insects, and examining the effect of seasonality. We investigate the outcome for pest control for which the plant-incorporated toxins are not necessarily at a high dose (i.e., they might not kill all homozygous susceptible and all heterozygous insects). We demonstrate that a RIDL-based approach could form an effective component of a resistance management strategy in a wide range of genetic and ecological circumstances. Because there are significant threshold effects for several variables, we expect that a margin of error would be advisable in setting release ratios and refuge sizes, especially as the frequency and properties of resistant alleles may be difficult to measure accurately in the field.
authors.affiliation: Mathematical Ecology Research Group, Department of Zoology, University of Oxford, South Parks Rd., Oxford OX1 3PS, United Kingdom.
authors.forename: Nina
authors.initials: N
authors.lastname: Alphey
authors.forename: Michael B
authors.initials: MB
authors.lastname: Bonsall
authors.forename: Luke
authors.initials: L
authors.lastname: Alphey
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics*; D003198:Computer Simulation; D018556:Crops, Agricultural / Q000235:genetics*; D004731:Endotoxins / Q000235:genetics*; D006460:Hemolysin Proteins / Q000235:genetics*; D007300:Insect Control / Q000379:methods; D007313:Insecta / Q000235:genetics* / Q000502:physiology; D007305:Insecticide Resistance / Q000235:genetics*; D008954:Models, Biological; D030781:Organisms, Genetically Modified; D012098:Reproduction / Q000235:genetics
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis