title: The impact of secondary pests on Bacillus thuringiensis (Bt) crops.
abstract: The intensification of agriculture and the development of synthetic insecticides enabled worldwide grain production to more than double in the last third of the 20th century. However, the heavy dependence and, in some cases, overuse of insecticides has been responsible for negative environmental and ecological impacts across the globe, such as a reduction in biodiversity, insect resistance to insecticides, negative effects on nontarget species (e.g. natural enemies) and the development of secondary pests. The use of recombinant DNA technology to develop genetically engineered insect-resistant crops could mitigate many of the negative side effects of insecticides. One such genetic alteration enables crops to express toxic crystalline (Cry) proteins from the soil bacteria Bacillus thuringiensis (Bt). Despite the widespread adoption of Bt crops, there are still a range of unanswered questions concerning longer term agro-ecosystem interactions. For instance, insect species that are not susceptible to the expressed toxin can develop into secondary pests and cause significant damage to the crop. Here, we review the main causes surrounding secondary pest dynamics in Bt crops and the impact of such outbreaks. Regardless of the causes, if nonsusceptible secondary pest populations exceed economic thresholds, insecticide spraying could become the immediate solution at farmers' disposal, and the sustainable use of this genetic modification technology may be in jeopardy. Based on the literature, recommendations for future research are outlined that will help to improve the knowledge of the possible long-term ecological trophic interactions of employing this technology.
authors.affiliation: School of Agriculture, Policy and Development, University of Reading, Reading, UK.
authors.forename: Rui
authors.initials: R
authors.lastname: Catarino
authors.affiliation: Department of Public Governance and Sustainable Development, MODUL University, Vienna, Austria.
authors.forename: Graziano
authors.initials: G
authors.lastname: Ceddia
authors.affiliation: School of Agriculture, Policy and Development, University of Reading, Reading, UK.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Areal
authors.affiliation: School of Agriculture, Policy and Development, University of Reading, Reading, UK.
authors.forename: Julian
authors.initials: J
authors.lastname: Park
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics*; D018556:Crops, Agricultural / Q000235:genetics*; D004731:Endotoxins / Q000235:genetics*; D004787:Environmental Pollution / Q000517:prevention & control; D006460:Hemolysin Proteins / Q000235:genetics*; D006790:Host-Parasite Interactions; D007300:Insect Control / Q000379:methods*; D007313:Insecta / Q000502:physiology*; D007305:Insecticide Resistance; D030821:Plants, Genetically Modified
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Bacillus thuringiensis; ecological impact; genetically engineered insect resistance crops; pest outbreak; secondary pest